Damp smell yours truly had (5)
I believe the answer is:
humid
'damp' is the definition.
(I've seen this before)
'smell yours truly had' is the wordplay.
'smell' becomes 'hum' (something with a bad smell is 'humming').
'yours truly had' becomes 'I'd' ('I had', referring to the crossword setter).
'hum'+'id'='HUMID'
(Other definitions for humid that I've seen before include "Damp and warm" , "Warm and steamy" , "Close" , "Damp, steamy" , "Moist, warm (weather)" .)