Refuse youth leader support for study (4)
I believe the answer is:
deny
'refuse' is the definition.
('deny' can be a synonym of 'refuse')
'youth leader support for study' is the wordplay.
'youth leader' becomes 'y' (I've seen this in other clues).
'support for' says to put letters next to each other.
'study' becomes 'den' (I've seen this before).
'y' put after 'den' is 'DENY'.
(Other definitions for deny that I've seen before include "Refuse to give" , "Reject as false" , "Contradict, refuse" , "Negate" , "Gainsay" .)