Ass died carrying leader (10)
I believe the answer is:
dunderhead
'ass' is the definition.
(both can mean a stupid person)
'died carrying leader' is the wordplay.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'carrying' becomes 'under' (something under something else may be carrying it).
'leader' becomes 'head' (head is a kind of leader).
'd'+'under'+'head'='DUNDERHEAD'
(Other definitions for dunderhead that I've seen before include "fool" , "Ignoramus" , "Stupid person" , "dumbass?" , "Idiot" .)