Reg worked, wife got bigger (4)
I believe the answer is:
grew
'got bigger' is the definition.
(I've seen this in another clue)
'reg worked wife' is the wordplay.
'worked' indicates an anagram.
'wife' becomes 'w' (abbreviation).
'reg' is an anagram of 'gre'.
'gre'+'w'='GREW'
(Other definitions for grew that I've seen before include "Became larger" , "Got bigger" , "Developed, matured" , "Multiplied" , "Rose" .)