Symbol of a duke or earl (7)
I believe the answer is:
coronet
'symbol of a duke or earl' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coronet that I've seen before include "brass embellishment" , "Jewelled circlet for the head" , "sign of rank" , "Simple crown" , "emblem of rank" .)