Get hold of outlaw retreating (3)
I believe the answer is:
nab
'get hold of' is the definition.
(nab can mean to arrest or apprehend)
'outlaw retreating' is the wordplay.
'outlaw' becomes 'ban' (banning is a kind of outlawing).
'retreating' is a reversal indicator.
'ban' written backwards gives 'NAB'.
(Other definitions for nab that I've seen before include "Capture, catch" , "Catch (a felon)" , "Capture (slang)" , "Run in" , "Take" .)