Mischievous child and companion in old city home (6)
I believe the answer is:
urchin
'mischievous child' is the definition.
(urchin can mean a misbehaving child)
'companion in old city home' is the wordplay.
'companion' becomes 'ch' (Companion of Honour).
'in' indicates putting letters inside.
'old city' becomes 'ur' (ancient city state).
'home' becomes 'in' ('he's home' can mean 'he's in').
'ur'+'in'='urin'
'ch' going inside 'urin' is 'URCHIN'.
'and' acts as a link.
(Other definitions for urchin that I've seen before include "Marine invertebrate with spiny shells" , "Guttersnipe" , "poor mite" , "Monkey" , "Marine hedgehog" .)