Grimaced, working to a tiny fraction of an ounce (8)

I believe the answer is:

decigram

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'a tiny fraction of an ounce' is the definition.
I can't tell whether this definition defines the answer.

'grimaced working' is the wordplay.
'working' indicates anagramming the letters.
'grimaced' anagrammed gives 'DECIGRAM'.

'to' acts as a link.

Can you help me to learn more?

(Another definition for decigram that I've seen is " Grimaced about one tenth of a gram".)

I've seen this clue in The Guardian.

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