Errand boy takes a monthly payment for family (9)
I believe the answer is:
parentage
'family' is the definition.
(I've seen this before)
'errand boy takes a monthly payment' is the wordplay.
'errand boy' becomes 'page' (page is a kind of errand boy).
'takes' means one lot of letters goes inside another.
'monthly payment' becomes 'rent' (rent is often paid monthly).
'a'+'rent'='arent'
'page' enclosing 'arent' is 'PARENTAGE'.
'for' acts as a link.
(Other definitions for parentage that I've seen before include "Ancestry" , "Ancestors" , "Family origins" , "Who's your father (and mother)?" , "Extraction, descent" .)