"Tombstone" lawman Wyatt (4)
I believe the answer is:
earp
'tombstone lawman wyatt' 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 - - (US marshal)" , "Wyatt --, Tombstone lawman" , "See 4 Across" , "Wyatt -, renowned US lawman" , "Wyatt --, US law officer" .)