Instrument returned for neighbour (4)
I believe the answer is:
abut
'for neighbour' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for abut that I've seen before include "Cease (from activity)" , "Adjoin, be contiguous to" , "Impinge" , "Touch, lean on" , "Meet" .)