Desire back massage before noon (4)
I believe the answer is:
burn
'desire' is the definition.
(thesaurus)
'back massage before noon' is the wordplay.
'back' says the letters should be written backwards.
'massage' becomes 'rub' (rub can mean to massage).
'before' says to put letters next to each other.
'noon' becomes 'n' (abbreviation for noon).
'rub' reversed gives 'bur'.
'bur'+'n'='BURN'
(Other definitions for burn that I've seen before include "Scottish brook" , "Small stream in Scotland" , "Scorch; brook" , "Catch light; stream" , "runner?" .)