Screw up and down (5)
I believe the answer is:
fluff
This clue is a double definition.
'screw up' is the first definition.
(both can mean to mess something up)
'down?' is the second definition.
(down can mean bird feathers)
'and' acts as a link.
(Other definitions for fluff that I've seen before include "Nap" , "Light downy substance - mistake?" , "Soft downy substance - bungle it" , "blooper" , "Botch" .)