Nasty smell in London area -- get cleaner (6)
I believe the answer is:
sponge
'cleaner' is the definition.
'nasty smell in london area' is the wordplay.
'nasty smell' becomes 'pong' (I've seen this before).
'in' means one lot of letters goes inside another.
'london area' becomes 'se' (abbreviation for South East).
'pong' inserted inside 'se' is 'SPONGE'.
'get' is the link.
(Other definitions for sponge that I've seen before include "Aquatic invertebrate -- type of cake" , "drunkard or > hanger-on" , "Freeload" , "Absorbing" , "Soft aquatic creature" .)