Flipping chose to keep at firm (9)
I believe the answer is:
dedicated
'firm' is the definition.
(firm can mean dedicated or committed)
'flipping chose to keep at' is the wordplay.
'flipping' says the letters should be written backwards.
'chose' becomes 'decided'.
'to keep' is an insertion indicator.
'decided' backwards is 'dediced'.
'dediced' enclosing 'at' is 'DEDICATED'.
(Other definitions for dedicated that I've seen before include "Committed" , "Customised" , "Devoted to a cause or ideal 99)" , "Hard working" , "Devoted to a particular cause or purpose" .)