Upgrade a perfume (6)
I believe the answer is:
ascent
'upgrade' is the definition.
('ascent' can be a synonym of 'upgrade')
'a perfume' is the wordplay.
'perfume' becomes 'scent' ('scent' can be a synonym of 'perfume').
'a'+'scent'='ASCENT'
(Other definitions for ascent that I've seen before include "way up the mountain" , "Upwards motion" , "rising?" , "Going up" , "Mountain path" .)