Extraordinary fat Austrian composer, a pain (14)

I believe the answer is:

flabbergasting

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'extraordinary fat austrian composer a pain' is the definition.
I can't tell whether this definition defines the answer.

'fat austrian composer a pain' is the wordplay.
'fat' becomes 'flab' (flab is a kind of fat).
'austrian composer' becomes 'berg' (I've seen this before).
'pain' becomes 'sting' (sting is a kind of pain).
'flab'+'berg'+'a'+'sting'='FLABBERGASTING'

Can you help me to learn more?

I've seen this clue in The Telegraph.

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