Why endlessly consume grain? (5)
I believe the answer is:
wheat
'grain?' is the definition.
(I know that wheat is a type of grain)
'why endlessly consume' is the wordplay.
'endlessly' means to remove the last letter.
'consume' becomes 'eat' (eating is a kind of consuming).
'why' with its last letter taken away is 'wh'.
'wh'+'eat'='WHEAT'
(Other definitions for wheat that I've seen before include "Cereal grass" , "Cereal grain" , "Cereal crop" , "(Pasta) cereal" , "Tall grass producing light brown grain" .)