Disintegration or noise, possibly (7)
I believe the answer is:
erosion
'disintegration' is the definition.
(I've seen this before)
'or noise possibly' is the wordplay.
'possibly' is an anagram indicator.
'or'+'noise'='ornoise'
'ornoise' is an anagram of 'EROSION'.
(Other definitions for erosion that I've seen before include "Action of wearing away" , "The wearing away as by wind or water" , "Gradual decline" , "The wearing away by weather 97)" , "dying away" .)