Study rigorous contract (9)
I believe the answer is:
constrict
'contract' is the definition.
('constrict' can be a synonym of 'contract')
'study rigorous' is the wordplay.
'study' becomes 'con' (I've seen this before).
'rigorous' becomes 'strict' ('strict' can be a synonym of 'rigorous').
'con'+'strict'='CONSTRICT'
(Other definitions for constrict that I've seen before include "Pinch" , "Compress" , "Limit" , "Cramp tightly" , "Strangle" .)