Make sick (8)
I believe the answer is:
nauseate
'make sick' is the definition.
(synonyms)
This is all the clue.
(Other definitions for nauseate that I've seen before include "Sicken" , "Make to feel imminent sickness, turn stomach" , "Make to feel sick, revolt" , "Cause sick or disgusted feeling" , "Cause to feel sick" .)