Study before exam or competition (7)
I believe the answer is:
contest
'competition' is the definition.
(synonyms)
'study before exam' is the wordplay.
'study' becomes 'con' (con can informally mean to study).
'before' means one lot of letters go next to another.
'exam' becomes 'test' (synonyms).
'con'+'test'='CONTEST'
'or' acts as a link.
(Other definitions for contest that I've seen before include "Competition; dispute" , "Competition or conflict" , "Oppose - competition" , "Tournament" , "Match" .)