In Latin, to a sickening extent (2,7)
I believe the answer is:
ad nauseam
'to a sickening extent' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ad nauseam that I've seen before include "seasickness pills like this would be counterproductive?" , "On and on - would make you sick" , "to an excessive extent" , "Past the stage of enjoying" , "To a very tiresome degree" .)