Hassle about last poor opera (8)

I believe the answer is:

falstaff

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'opera' is the definition.
(Verdi opera)

'hassle about last poor' is the wordplay.
'hassle' becomes 'faff' (I can't explain this - if you can you should believe this answer much more).
'about' indicates putting letters inside.
'poor' indicates anagramming the letters.
'last' is an anagram of 'lsta'.
'faff' going around 'lsta' is 'FALSTAFF'.

Can you help me to learn more?

(Other definitions for falstaff that I've seen before include "stout fellow" , "Mendacious Shakespearean knight" , "from 6 &12 [VERDI & SHAKESPEARE] ?" , "Debauched character" , "Rogue knight" .)

I've seen this clue in The Times and The Sunday Times.

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