Firm sauce served up for cat (6)
I believe the answer is:
cougar
'for cat' is the definition.
(cougar is a kind of cat)
'firm sauce served up' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'sauce' becomes 'ragu' (I've seen this before).
'served up' says the letters should be written backwards (in a down clue, going upwards).
'ragu' in reverse letter order is 'ugar'.
'co'+'ugar'='COUGAR'
(Other definitions for cougar that I've seen before include "Cat, aka puma" , "N American mountain lion, puma" , "American wildcat, puma" , "Another name for puma" , "Big cat" .)