Firm dates chopped up quickly (9)
I believe the answer is:
steadfast
'firm' is the definition.
(I know that firm can be written as steadfast)
'dates chopped up quickly' is the wordplay.
'chopped up' indicates an anagram.
'quickly' becomes 'fast' (synonyms).
'dates' anagrammed gives 'stead'.
'stead'+'fast'='STEADFAST'
(Other definitions for steadfast that I've seen before include "stable" , "Constant; true" , "Constant and resolute" , "Firm, fixed and faithful" , "Dedicated" .)