A cold, man? Just take an aspirin for it! (4)
I believe the answer is:
ache
'take an aspirin for it' is the definition.
(I've seen this before)
'a cold man?' is the wordplay.
'cold' becomes 'C' (eg on taps).
'man?' becomes 'he' (he refers to a man).
'a'+'c'+'he'='ACHE'
'just' acts as a link.
(Other definitions for ache that I've seen before include "Cause pain" , "suffering" , "Dull prolonged pain" , "Nagging pain" , "strong feeling" .)