Rotten page note on the subject of perfume (10)
I believe the answer is:
putrescent
'rotten' is the definition.
(thesaurus)
'page note on the subject of perfume' is the wordplay.
'page' becomes 'p'.
'note on' becomes 'ut' (I've seen this in other clues. I am not sure about the 'on' bit.).
'the subject of' becomes 're' ('re' means regarding or about).
'perfume' becomes 'scent' (synonyms).
'p'+'ut'+'re'+'scent'='PUTRESCENT'
(Other definitions for putrescent that I've seen before include "Decaying, rotting" , "High" .)