Fine officer has broken cover (7)
I believe the answer is:
shelter
'cover' is the definition.
(I've seen this in another clue)
'fine officer has broken' is the wordplay.
'fine' becomes 'sheer' (I've seen this before).
'officer' becomes 'lt' (abbreviation for lieutenant).
'has broken' means one lot of letters goes inside another (inserted letters break in).
'sheer' placed around 'lt' is 'SHELTER'.
(Other definitions for shelter that I've seen before include "Protective structure" , "Sanctuary, protection" , "Protection; charity for the homeless" , "Place of refuge" , "Housing or haven" .)