Bird fabled to devastate much corn (3)
I believe the answer is:
roc
'bird' is the definition.
(mythological bird of prey)
'devastate much corn' is the wordplay.
'devastate' indicates anagramming the letters (I've seen 'devastated' mean this (devastate literally means destroy or lay waste to)).
'much' means to remove the last letter (much but not all of the word).
'corn' with its last letter taken away is 'cor'.
'cor' is an anagram of 'ROC'.
'fabled to' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for roc that I've seen before include "Gigantic bird of Arabian legend" , "Enormous, mythical bird of prey" , "Arabian Nights bird" , "Huge mythical bird of prey" , "Legendary thing" .)