Embarrassed top MP (6)
I believe the answer is:
redcap
'mp' is the definition.
(redcap is a kind of mp)
'embarrassed top' is the wordplay.
'embarrassed' becomes 'red' (I've seen this before).
'top' becomes 'cap' (cap is a kind of top).
'red'+'cap'='REDCAP'
(Other definitions for redcap that I've seen before include "Carped (anag)" , "MP" , "Military policeman (slang)" , "Goldfinch" , "Mil. policeman (colloq.)" .)