Work as printer in family firm (7)
I believe the answer is:
typeset
'work as printer' is the definition.
'family firm' is the wordplay.
'family' becomes 'type'.
'firm' becomes 'set' (I've seen this before).
'type'+'set'='TYPESET'
'in' acts as a link.
(Other definitions for typeset that I've seen before include "(Of fonts) ready to print" , "Arrange (text) for printing" , "characters lined up ready for a run-off?" , "Ready to be printed" , "Ready to go public" .)