Expert in fix, under threat (7)

I believe the answer is:

menaced

'under threat' is the definition.
(menace can mean to threaten)

'expert in fix' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'in' means one lot of letters goes inside another.
'fix' becomes 'mend' (synonyms).
'ace' going within 'mend' is 'MENACED'.

(Another definition for menaced that I've seen is " Threatened".)

I've seen this clue in The Guardian.

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