Study decapitated religious figure (3)
I believe the answer is:
con
'study' is the definition.
(con can informally mean to study)
'decapitated religious figure' is the wordplay.
'decapitated' means to remove the first letter.
'religious figure' becomes 'icon' (I've seen this in another clue).
'icon' with its initial letter taken away is 'CON'.
(Other definitions for con that I've seen before include "Study - trick" , "Study; steer" , "Learn; swindle" , "Deception; disadvantage" , "Not in favour" .)