Old West lawman (4)
I believe the answer is:
earp
'old west lawman' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for earp that I've seen before include "Wyatt --, Tombstone lawman" , "Wyatt -, renowned US lawman" , "Wyatt - (O.K. Corral)" , "Wyatt --, US law officer" , "Wyatt - - (US marshal)" .)