Answer: deteriorate

AnswerCrossword Clue
DETERIORATEImpair.
DETERIORATEIt has "rot" and "die" inside
DETERIORATEWaste away
DETERIORATEGo downhill
DETERIORATE"Go downhill and stop," I pontificate (11)
DETERIORATESlide
deteriorateto make inferior in quality or value
deteriorateBecome progressively worse