Deteriorate through neglect (2,2,3)
I believe the answer is:
go to pot
'deteriorate through neglect' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for go to pot that I've seen before include "Approach snooker table" , "If you want a cup of tea" , "Decline" , "crumble?" , "fail badly" .)