Fury endless in downmarket newspaper (3)
I believe the answer is:
rag
'downmarket newspaper' is the definition.
'rag' can be an answer for 'newspaper' (informal term for a newspaper). I'm not sure about the 'downmarket' bit.
'fury endless' is the wordplay.
'fury' becomes 'rage' (synonyms).
'endless' means to remove the last letter.
'rage' with its last letter taken away is 'RAG'.
'in' is the link.
Can you help me to learn more?
(Other definitions for rag that I've seen before include "Waste piece of cloth" , "Scrap; newspaper (derog.)" , "Student carnival for charity" , "Piece of cloth and student fun" , "Disreputable newspaper" .)