Make out that cinders are sifted (7)
I believe the answer is:
discern
'make out' is the definition.
(synonyms)
'cinders are sifted' is the wordplay.
'are sifted' indicates an anagram.
'cinders' anagrammed gives 'DISCERN'.
'that' is the link.
(Other definitions for discern that I've seen before include "Recognise, find out" , "Detect" , "Espy" , "Make out, distinguish by eye" , "spot" .)