London borough cut back foreign money (7)
I believe the answer is:
hackney
'london borough' is the definition.
(I've seen this before)
'cut back foreign money' is the wordplay.
'cut' becomes 'hack' (hacking is a kind of cutting**).
'back' says the letters should be written backwards.
'foreign money' becomes 'yen' (Japanese currency).
'yen' in reverse letter order is 'ney'.
'hack'+'ney'='HACKNEY'
(Other definitions for hackney that I've seen before include "draught horse" , "Carriage for hire" , "Old cab - London borough" , "Wear out" , "A kind of taxi or car for hire" .)