Son coming into clean wealth (5)
I believe the answer is:
purse
'wealth' is the definition.
(thesaurus)
'son coming into clean' is the wordplay.
'son' becomes 's'.
'coming into' is an insertion indicator.
'clean' becomes 'pure' ('pure' can be similar in meaning to 'clean').
's' placed inside 'pure' is 'PURSE'.
(Other definitions for purse that I've seen before include "Knit" , "Money holder" , "Shakespeare 'Put money in thy . . . . .'" , "Money bag; pucker" , "Contract, crease" .)