Son with time becomes wise (4)
I believe the answer is:
sage
'wise' is the definition.
(similar in meaning)
'son with time' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'with' means one lot of letters go next to another.
'time' becomes 'age' (an age is a period of time).
's'+'age'='SAGE'
'becomes' is the link.
(Other definitions for sage that I've seen before include "cheesemongers associate with Derby" , "Wise man - flavoursome plant" , "Clary" , "Aromatic herb" , "Profoundly wise" .)