Agree to study mould (7)
I believe the answer is:
conform
'agree' is the definition.
(conforming is a kind of agreeing)
'study mould' is the wordplay.
'study' becomes 'con' (I've seen this before).
'mould' becomes 'form' ('form' can be a synonym of 'mould').
'con'+'form'='CONFORM'
'to' acts as a link.
(Other definitions for conform that I've seen before include "Comply with accepted rules" , "become fitter?" , "Follow the crowd" , "Toe the line" , "Fall into line" .)