Works by Verdi possibly upset a poser (6)
I believe the answer is:
operas
'works by verdi' is the definition.
'operas' can be an answer for 'works' (I have seen 'Musical works' mean 'operas' so perhaps 'works' could also mean 'operas'). I'm unsure of the 'by verdi' bit.
'upset a poser' is the wordplay.
'upset' is an anagram indicator.
'a'+'poser'='aposer'
'aposer' is an anagram of 'OPERAS'.
'possibly' is the link.
Can you help me to learn more?
(Other definitions for operas that I've seen before include "Plays in which the words are sung" , "'La Boheme and La Traviata, say (6)'" , "Musical dramas" , "O spare these dramas" , "Musical plays" .)