Love's put on dreary perfume (5)
I believe the answer is:
odour
'perfume' is the definition.
(I've seen this before)
'love's put on dreary' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'put on' says to put letters next to each other.
'dreary' becomes 'dour' (I've seen this before).
'o'+'dour'='ODOUR'
(Other definitions for odour that I've seen before include "Any property detected by the olfactory system" , "Distinctive smell" , "A smell, good or bad" , "Stink" , "Nasty smell" .)