Clue: Writer was angry, maybe about Thackeray hero (9)
Answer: PENDENNIS
Explanation: Definition: Writer

**PEN** ("writer") + **<=SINNED** ("was angry", *about*), wrath being one of the seven deadly sins.
 

 
*"Pendennis" is the eponymous character of a Thackeray novel, published in 1848.