Repeated thanks to the two who entered clues for WITCH. My opinions are below, with the result nethermost.
Luciano
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Duke:
Woman working her magic saw it change a bit (5)
Hidden in SAW IT CHANGE; def = woman working her magic
-- ‘a bit’ on its own doesn’t do it for me as hidden word indicator. ‘a bit of’ (preceding the fodder) would certainly work, but fitting that into this clue would be somewhat difficult.
Jerk takes top off weird sister (5)
(t)WITCH; def = weird sister
-- I like this one, even if the surface is a little troubling. The idea of TWITCH taking its own top off is reasonable enough to me.
Mean lady will start to wail before long (5)
W(ail) + ITCH; def = mean lady
-- My main objection to this clue is ‘will’. It doesn’t seem to be doing anything. Otherwise, good.
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Steve:
She spells 'twitch' without one of the 't's (5)
(t)WITCH; def = she spells
-- Pretty good (the ‘spelling’ business is clever), though perhaps a bit too obvious with ‘twitch’ staring us in the face.
or, in a…twist:
She spells 'twitch' incorrectly, without one of the 't's (5)
TWI(t)CH anag ('incorrectly'); def = she spells
-- See previous comment.
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The winner is Duke with his weird sister clue.