Nausea (8)
I believe the answer is:
sickness
'nausea' is the definition.
(I know that nausea can be written as sickness)
This is all the clue.
(Other definitions for sickness that I've seen before include "Ill health" , "Ailment" , "Illness, malady" , "It's not looking good" , "Illness, disease" .)