In panic, if retired, shaking (9)

I believe the answer is:

terrified

I'm a little stuck... Click here to teach me more about this clue!

'in panic if retired shaking' is the definition.
I can't judge whether this defines the answer.

'if retired shaking' is the wordplay.
'shaking' indicates anagramming the letters.
'if'+'retired'='ifretired'
'ifretired' with letters rearranged gives 'TERRIFIED'.

Can you help me to learn more?

(Other definitions for terrified that I've seen before include "Extremely frightened" , "Panic-stricken - dire refit (anag)" , "Greatly frightened" , "Scared stiff" .)

I've seen this clue in The Guardian.

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