Man smelled no potassium (4)
I believe the answer is:
stan
'man' is the definition.
'smelled no potassium' is the wordplay.
'smelled' becomes 'stank' (stinking is a kind of smelling).
'no' is a deletion indicator.
'potassium' becomes 'K' (K is the chemical symbol for potassium).
'stank' with 'k' taken out is 'STAN'.
(Other definitions for stan that I've seen before include "Ollie's partner" , "Eminem hit; man's name" , "- Laurel, Hardy's partner" , "guy" , "- Laurel, comedian" .)