Military policeman (6)
I believe the answer is:
redcap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military policeman</span>' is the definition.<br/ ><span class="explanation-format__explanation">(redcap is a kind of military policeman)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for redcap that I've seen before include "MP" , "Member of the military police" , "Carped (anag)" , "Mil. policeman (colloq.)" , "bird!" .)