Seasick feeling (6)
I believe the answer is:
nausea
'seasick feeling' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nausea that I've seen before include "Feeling of sickness or disgust" , "A feeling of disgust or illness" , "Queasy feeling" , "Feeling of imminent sickness or upset stomach" , "Seasickness" .)