Policeman is worried by initially cautious cooperation (10)
I believe the answer is:
compliance
'cooperation' is the definition.
(compliance is a kind of cooperation)
'policeman is worried by initially cautious' is the wordplay.
'is worried' indicates anagramming the letters.
'by' is a charade indicator (letters next to each other).
'initially' suggests taking the first letters.
The initial letter of 'cautious' is 'c'.
'policeman' anagrammed gives 'ompliance'.
'ompliance' after 'c' is 'COMPLIANCE'.
(Other definitions for compliance that I've seen before include "submissiveness" , "Agreement" , "submission" , "deference" .)