Make out that cinders need sifting (7)

I believe the answer is:

discern

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'make out' is the definition.
(I know that make out can be written as discern)

'cinders need sifting' is the wordplay.
'cinders' can be anagrammed to 'DISCERN'.
Though, I'm not clear how this is indicated.

'that' acts as a link.

Can you help me to learn more?

(Other definitions for discern that I've seen before include "See" , "Cinders (anag)" , "Pick out" , "spot" , "Recognise, find out" .)

I've seen this clue in the Evening Standard.

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