It may fly in endless rage (3)
I believe the answer is:
fur
'it may fly' is the definition.
(reference to the phrase 'make the fur fly')
'endless rage' is the wordplay.
'endless' means to remove the last letter.
'rage' becomes 'fury' ('fury' can be a synonym of 'rage').
'fury' with its last letter removed is 'FUR'.
'in' acts as a link.
(Other definitions for fur that I've seen before include "Animal pelt" , "Expensive coat; deposit in kettle" , "Animal skin like mink or sable" , "eg Cat's coat" , "Coating in kettle" .)