Crossword Genius

Flock mistakenly got grain once (12)

Ross

I believe the answer is:

congregation

'flock' is the definition.
(thesaurus)

'mistakenly got grain once' is the wordplay.
'mistakenly' indicates anagramming the letters.
'got'+'grain'+'once'='gotgrainonce'
'gotgrainonce' is an anagram of 'CONGREGATION'.

(Other definitions for congregation that I've seen before include "Group assembling for worship" , "Group of worshippers" .)

I've seen this clue in The Telegraph.
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