Study with severe cramp (9)
I believe the answer is:
constrict
'cramp' is the definition.
(I've seen this before)
'study with severe' is the wordplay.
'study' becomes 'con' (con can informally mean to study).
'with' means one lot of letters go next to another.
'severe' becomes 'strict' (I've seen this in another clue).
'con'+'strict'='CONSTRICT'
(Other definitions for constrict that I've seen before include "press" , "Make narrower" , "Cramp tightly" , "narrow?" , "Strangulate" .)