Upper-class lady against benefit being raised (8)
I believe the answer is:
contessa
'upper-class lady' is the definition.
(an Italian countess)
'against benefit being raised' is the wordplay.
'against' becomes 'con' (as in pros and cons, for and against).
'benefit' becomes 'asset' (I've seen this before).
'being raised' says the letters should be written backwards (going up in a down clue).
'asset' backwards is 'tessa'.
'con'+'tessa'='CONTESSA'
(Other definitions for contessa that I've seen before include "foreign noblewoman" , "Italian noblewoman" , "Italian lady" , "European noble" , "High-ranking female" .)