Noise is unfortunate result (6)
I believe the answer is:
rustle
'noise' is the definition.
(rustle is a kind of noise)
'unfortunate result' is the wordplay.
'unfortunate' indicates an anagram.
'result' with letters rearranged gives 'RUSTLE'.
'is' acts as a link.
(Other definitions for rustle that I've seen before include "Make sound as of paper crumpling - or steal cattle" , "The sound of leaves in the wind" , "Result (anag.)" , "Steal ((eg, cattle)" , "Swish - lustre (anag)" .)