Old fighter with fiery temper (8)
I believe the answer is:
spitfire
This might be a double definition.
'old fighter' is the first definition.
(historical type of fighter plane)
'fiery temper' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'with' acts as a link.
(Other definitions for spitfire that I've seen before include "British fighter plane of WW2, or a fiery-tempered person" , "WW2 fighter aircraft" , "RAF WW2 fighter" , "Fighter aircraft in WWII" , "Quick-tempered person" .)