Charlie soon to become a clergyman (5)
I believe the answer is:
canon
'a clergyman' is the definition.
(canon is a kind of clergyman)
'charlie soon' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'soon' becomes 'anon' (synonyms).
'c'+'anon'='CANON'
'to become' is the link.
(Other definitions for canon that I've seen before include "Principle - member of cathedral staff" , "Principle; list of recognised works" , "Criterion; church official" , "collected works" , "Churchman" .)