Lit fuel following discharge, which is vindictive (8)
I believe the answer is:
spiteful
'is vindictive' is the definition.
(I've seen this in another clue)
'lit fuel following discharge' is the wordplay.
'lit' indicates anagramming the letters (lit can mean drunk).
'following' says to put letters next to each other.
'discharge' becomes 'spit' (saliva discharged from the mouth).
'fuel' with letters rearranged gives 'eful'.
'eful' put after 'spit' is 'SPITEFUL'.
'which' acts as a link.
(Other definitions for spiteful that I've seen before include "Catty" , "nasty!" , "With desire to hurt" , "Vindictive - malicious" , "Vengeful, malicious" .)