MP died during summing up (6)
I believe the answer is:
redcap
'mp' is the definition.
(redcap is a kind of mp)
'died during summing up' is the wordplay.
'died' becomes 'd'.
'during' indicates putting letters inside.
'summing up' becomes 'recap'.
'd' placed inside 'recap' is 'REDCAP'.
(Other definitions for redcap that I've seen before include "Member of the military police" , "Carped (anag)" , "Hole from explosion" , "Mil. policeman (colloq.)" , "Goldfinch" .)