Last month, one year after producing rot (5)
I believe the answer is:
decay
'rot' is the definition.
(thesaurus)
'last month one year after producing' is the wordplay.
'last month' becomes 'dec'.
'one year' becomes 'y'.
'after' is a charade indicator (letters next to each other).
'producing' becomes 'a' (I can't justify this - if you can you should believe this answer much more).
'y' put after 'a' is 'ay'.
'dec'+'ay'='DECAY'
Can you help me to learn more?
(Other definitions for decay that I've seen before include "Decompose or fall into ruin" , "'Decompose, rot (5)'" , "Briefly fashionable" , "Rot, perish" , "Putrefy" .)