North America's first exploit precedes a feeling of revulsion (6)
I believe the answer is:
nausea
'a feeling of revulsion' is the definition.
(I've seen this before)
'north america's first exploit precedes' is the wordplay.
'north america' becomes 'na'.
'first' becomes 'a'.
'exploit' becomes 'use' (use is a kind of exploit**).
'precedes' says to put letters next to each other.
'a' after 'use' is 'usea'.
'na'+'usea'='NAUSEA'
(Other definitions for nausea that I've seen before include "Feeling of sickness or disgust" , "Feeling of imminent sickness or upset stomach" , "Sick feeling" , "Seasickness" , "Sickness, biliousness" .)