Noise is unusual result (6)
I believe the answer is:
rustle
'noise' is the definition.
(I know that rustle is a type of noise)
'unusual result' is the wordplay.
'unusual' indicates an anagram.
'result' anagrammed gives 'RUSTLE'.
'is' is the link.
(Other definitions for rustle that I've seen before include "The sound of leaves in the wind" , "Swish - steal cattle" , "Swish - lustre (anag)" , "take animals" , "Make sound as of paper crumpling - or steal cattle" .)