Military policeman's discussion about east Washington area (6)
I believe the answer is:
redcap
'military policeman's' is the definition.
(redcap is a kind of military policeman)
'discussion about east washington area' is the wordplay.
'discussion' becomes 'rp' (I can't explain this - if you can you should believe this answer much more).
'about' means one lot of letters goes inside another.
'east' becomes 'e' (abbreviation).
'washington' becomes 'dc' (Washington DC).
'area' becomes 'a' (maths abbreviation).
'e'+'dc'+'a'='edca'
'rp' enclosing 'edca' is 'REDCAP'.
Can you help me to learn more?
(Other definitions for redcap that I've seen before include "Hole from explosion" , "Military policeman (slang)" , "Member of the military police" , "Carped (anag)" , "Goldfinch" .)