Smell old drunk (6)
I believe the answer is:
stinko
'drunk' is the definition.
(I've seen this before)
'smell old' is the wordplay.
'smell' becomes 'stink' (stink is a kind of smell**).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'stink'+'o'='STINKO'
(Other definitions for stinko that I've seen before include "Tight" , "Drunk" , "worse for wear" , "one over the eight?" .)