Catch neighbour attempting burglary, initially (3)
I believe the answer is:
nab
'catch' is the definition.
(nab can mean to capture or arrest)
'neighbour attempting burglary initially' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'neighbour attempting burglary' is 'NAB'.
(Other definitions for nab that I've seen before include "Catch; grab suddenly" , "Pinch" , "Capture, catch" , "Apprehend" , "Catch (thief) (colloq.)" .)