Eastern city hack houses new family (7)
I believe the answer is:
nanking
'eastern city' is the definition.
(I've seen this before)
'hack houses new family' is the wordplay.
'hack' becomes 'nag' (synonyms).
'houses' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'family' becomes 'kin' (synonyms).
'n'+'kin'='nkin'
'nag' going around 'nkin' is 'NANKING'.
(Other definitions for nanking that I've seen before include "Port" , "Eastern city" , "Oriental city" , "Chinese city" .)