Mess up and down (5)
I believe the answer is:
fluff
I believe this is a double definition.
'mess up' is the first definition.
('fluff' can be a synonym of 'mess up')
'down' is the second definition.
(thesaurus)
'and' is the link.
(Other definitions for fluff that I've seen before include "Make a mistake" , "Trifling" , "mistake made by some player in action?" , "Error" , "The fuzz" .)