Bouncer in city house (4)
I believe the answer is:
echo
'bouncer' is the definition.
(echoes bounce off things)
'city house' is the wordplay.
'city' becomes 'EC' (the City of London postcode).
'house' becomes 'ho' (abbreviation for house).
'ec'+'ho'='ECHO'
'in' is the link.
(Other definitions for echo that I've seen before include "Comms code word for E" , "Reflection of sound waves" , "Audio effect" , "Be suggestive of" , "Sound bouncing back" .)