One may be still due for some satisfaction (8)
I believe the answer is:
duellist
'some satisfaction' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'one may be still due' is the wordplay.
'one may be' indicates an anagram.
'still'+'due'='stilldue'
'stilldue' anagrammed gives 'DUELLIST'.
'for' is the link.
Can you help me to learn more?
(Other definitions for duellist that I've seen before include "Person engaged in single combat" , "one fighting on a point of honour" , "Fighter" , "Combatant in deadly fight between two people" , "he calls one out" .)