Unappreciative chap lighting fire here? (7)
I believe the answer is:
ingrate
'unappreciative chap' is the definition.
(an ungrateful person)
I don't understand how the rest of the clue works.
(Other definitions for ingrate that I've seen before include "One unappreciative" , "Unappreciative type" , "No thanks, I say!" , "One who never says thanks" , "Thankless wretch" .)