Shellfish not in extract? (6,3)

I believe the answer is:

winkle out

'extract?' is the definition.
(thesaurus)

'shellfish not in' is the wordplay.
'shellfish' becomes 'winkle' (winkle is a kind of shellfish).
'not in' becomes 'out' ('out' is the opposite to 'in').
'winkle'+'out'='WINKLE OUT'

(Another definition for winkle out that I've seen is " Extract with some difficulty".)

I've seen this clue in The Telegraph.

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