Military policeman in preferred capacity (6)

I believe the answer is:

redcap

'military policeman' is the definition.
(redcap is a kind of military policeman)

'in preferred capacity' is the wordplay.
'in' indicates the answer is hidden within the clue.
'REDCAP' is hidden in the letters of 'preferred capacity'.

(Other definitions for redcap that I've seen before include "Military policeman (slang)" , "bird!" , "Carped (anag)" , "Member of the military police" , "MP" .)

I've seen this clue in The Times.

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