Rent to the navy (4)
I believe the answer is:
torn
'rent' is the definition.
('torn' can be a synonym of 'rent')
'to the navy' is the wordplay.
'the navy' becomes 'rn' (abbreviation for Royal Navy).
'to'+'rn'='TORN'
(Other definitions for torn that I've seen before include "Dance wear" , "Ragged" , "Ripped - undecided" , "Divided" , "?Curtain (Hitchcock thriller)" .)