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 anagramming the letters.
'result' with letters rearranged gives 'RUSTLE'.
'is' is the 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)" .)