Females opening have to cut mistakes (5)
I believe the answer is:
muffs
'mistakes' is the definition.
(muff is a kind of mistake)
'females opening have to cut' is the wordplay.
'females' becomes 'ff' (I've seen this in other clues).
'opening' indicates putting letters inside (some letters open a gap in others).
'have to' becomes 'must' (I've seen this before).
'cut' means to remove the last letter.
'must' with its final letter taken away is 'mus'.
'ff' put inside 'mus' is 'MUFFS'.
(Other definitions for muffs that I've seen before include "Hand-warmers" , "Deals clumsily with" , "hand warmers" .)