Borrow, but not really (3)
I believe the answer is:
bum
'borrow but not really' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bum that I've seen before include "US tramp" , "False" , "American hobo or vulgar bottom" , "American hobo or English bottom" , "American hobo or vulgar backside" .)