Decay, disintegrate (9)
I believe the answer is:
decompose
This clue is a double definition.
'decay' is the first definition.
(I know that decay can be written as decompose)
'disintegrate' is the second definition.
(I know that disintegrate can be written as decompose)
(Other definitions for decompose that I've seen before include "Rot" , "Crumble" , "Break down" , "Decay, disintegrate" , "Spoil" .)