Member of the clergy caught on immediately (5)
I believe the answer is:
canon
'member of the clergy' is the definition.
(type of clergyman)
'caught on immediately' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'on' means one lot of letters go next to another.
'immediately' becomes 'anon' (anon can mean soon or promptly).
'c'+'anon'='CANON'
(Other definitions for canon that I've seen before include "Rule -- principle" , "General rule; clergyman" , "religious leader" , "Such literary works are genuine" , "in the ministry" .)