Exclamation of disgust (3)
I believe the answer is:
ugh
'exclamation of disgust' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ugh that I've seen before include "How repulsive!" , "Exclamation of disgust arising from hug" , "It's revolting" , "Disgust in thought" , "Yuck (colloq.)" .)