Is able to accept a fife variation as stimulating! (7)

I believe the answer is:

caffein

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

'as stimulating' is the definition.
I can't judge whether this defines the answer.

'is able to accept a fife variation' is the wordplay.
'is able to' becomes 'can' (I've seen this before).
'accept' indicates putting letters inside.
'variation' indicates anagramming the letters.
'fife' anagrammed gives 'ffei'.
'can' going around 'ffei' is 'CAFFEIN'.

Can you help me to learn more?

(Another definition for caffein that I've seen is " Coffee ingredient (alt. spelling)".)

I've seen this clue in the Evening Standard.

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