I modified your code little bit and I got this error.

λ> :t (pure (+) <*> ([1, 2, 3] :: [Int]))
(pure (+) <*> ([1, 2, 3] :: [Int])) :: [Int -> Int]

λ> show (pure (+) <*> ([1, 2, 3] :: [Int]))

<interactive>:13:1:
    No instance for (Show (Int -> Int)) arising from a use of ‘show’
    In the expression: show (pure (+) <*> ([1, 2, 3] :: [Int]))
    In an equation for ‘it’:
        it = show (pure (+) <*> ([1, 2, 3] :: [Int]))

You have list of functions ( [Int -> Int] ) and functions are not instance of Show class so error is pointing towards this fact.

λ> :i Show
class Show a where
showsPrec :: Int -> a -> ShowS
show :: a -> String
showList :: [a] -> ShowS
    -- Defined in ‘GHC.Show’
instance Show a => Show [a] -- Defined in ‘GHC.Show’
instance Show Ordering -- Defined in ‘GHC.Show’
instance Show a => Show (Maybe a) -- Defined in ‘GHC.Show’
instance Show Integer -- Defined in ‘GHC.Show’
instance Show Int -- Defined in ‘GHC.Show’
instance Show Char -- Defined in ‘GHC.Show’
instance Show Bool -- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j, Show k, Show l, Show m, Show n, Show o) =>
         Show (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j, Show k, Show l, Show m, Show n) =>
         Show (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j, Show k, Show l, Show m) =>
         Show (a, b, c, d, e, f, g, h, i, j, k, l, m)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j, Show k, Show l) =>
         Show (a, b, c, d, e, f, g, h, i, j, k, l)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j, Show k) =>
         Show (a, b, c, d, e, f, g, h, i, j, k)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i, Show j) =>
         Show (a, b, c, d, e, f, g, h, i, j)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h, Show i) =>
         Show (a, b, c, d, e, f, g, h, i)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f, Show g,
          Show h) =>
         Show (a, b, c, d, e, f, g, h)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f,
          Show g) =>
         Show (a, b, c, d, e, f, g)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e, Show f) =>
         Show (a, b, c, d, e, f)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d, Show e) =>
         Show (a, b, c, d, e)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c, Show d) => Show (a, b, c, d)
-- Defined in ‘GHC.Show’
instance (Show a, Show b, Show c) => Show (a, b, c)
-- Defined in ‘GHC.Show’
instance (Show a, Show b) => Show (a, b) -- Defined in ‘GHC.Show’
instance Show () -- Defined in ‘GHC.Show’
instance (Show a, Show b) => Show (Either a b)
-- Defined in ‘Data.Either’
instance Show a => Show (ZipList a)
-- Defined in ‘Control.Applicative’
instance Show Float -- Defined in ‘GHC.Float’
instance Show Double -- Defined in ‘GHC.Float’

See the [1] [2].

[1] https://wiki.haskell.org/Show_instance_for_functions
[2] http://stackoverflow.com/questions/15823732/why-is-there-no-show-instance-for-functions