Not up to game in Kentish Town (9)
I believe the answer is:
tonbridge
'kentish town' is the definition.
(market town in kent)
'not up to game' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'to game' becomes 'bridge' (bridge is a kind of game).
'not' written backwards gives 'ton'.
'ton'+'bridge'='TONBRIDGE'
'in' is the link.
(Other definitions for tonbridge that I've seen before include "Public school" , "Town in Kent" , "Kentish Town" .)