Decompose (5)
'decompose' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for rot that I've seen before include "Rubbish (colloq.)" , "Decay, go bad" , "Decay or disintegrate" , "Deteriorate" , "Balderdash" .)
'decompose' is the definition.
(I know that decompose is a more specific form of decay)
This is all the clue.
(Other definitions for decay that I've seen before include "Decline, decompose" , "'Decompose, rot (5)'" , "Briefly fashionable" , "Decompose or fall into ruin" , "Deterioration" .)