Some mistake no-one accepted (5)
I believe the answer is:
taken
'one accepted' is the definition.
(I've seen this before)
'some mistake no' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'TAKEN' is hidden within 'mistake no'.
(Other definitions for taken that I've seen before include "Obtained" , "Kidnapped" , "This is spoken for" , "Transported" , "Seized" .)