Giant blunder on pitch disheartened Royle (4)
I believe the answer is:
ogre
'giant' is the definition.
(I've seen this before)
'blunder on pitch disheartened royle' is the wordplay.
'blunder on pitch' becomes 'og' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'disheartened' suggests removing the centre.
'royle' with its centre removed is 're'.
'og'+'re'='OGRE'
Can you help me to learn more?
(Other definitions for ogre that I've seen before include "One making giant strides" , "man-eater" , "Giant who eats people" , "Monstrous giant" , "Has a monstrous role" .)