Mother with child builder (5)
I believe the answer is:
mason
'builder' is the definition.
(I've seen this before)
'mother with child' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'with' is a charade indicator (letters next to each other).
'child' becomes 'son' (son is a kind of child).
'ma'+'son'='MASON'
(Other definitions for mason that I've seen before include "Secret society member" , "Stone-carver" , "Construction industry employee" , "Craftsperson who works with stone or brick" , "Dresser" .)