Neighbour with some brass coming back (4)
I believe the answer is:
abut
'neighbour' is the definition.
(I've seen this before)
'some brass coming back' is the wordplay.
'some brass' becomes 'tuba' (tuba is a kind of brass).
'coming back' is a reversal indicator.
'tuba' written backwards gives 'ABUT'.
'with' is the link.
(Other definitions for abut that I've seen before include "Be next to -- share a boundary" , "Adjoin, border" , "Adjoin at one end" , "Touch upon" , "Adjoin, touch" .)