Operative damaged conifer
I believe the answer is:
in force
'operative' is the definition.
('in force' can be similar in meaning to 'operative')
'damaged conifer' is the wordplay.
'damaged' indicates anagramming the letters.
'conifer' with letters rearranged gives 'IN FORCE'.
(Other definitions for in force that I've seen before include "policemen are" , "Bobby is" , "with large numbers" , "Legally operative" , "Effective" .)