Duelist Aaron (4)
I believe the answer is:
burr
'duelist aaron' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for burr that I've seen before include "Rough or dialectic pronunciation: rough edge on metal" , "Prickly seeds" , "impediment?" , "Seed carrying pod with hooks" , "English dialect sound - notorious US vice-president, charged with treason" .)