Boss demanding endless academic application (4)
I believe the answer is:
stud
'boss' is the definition.
('stud' can be a synonym of 'boss')
'endless academic application' is the wordplay.
'endless' means to remove the last letter.
'academic application' becomes 'study' (applying oneself academically).
'study' with its last letter removed is 'STUD'.
'demanding' is the link.
(Other definitions for stud that I've seen before include "seen in a boiled shirt" , "Decorative round-headed nail" , "Item designed to grip" , "Clothes fastener in horse establishment" , "Football boot peg" .)