Sickness that's a value in North America (6)
I believe the answer is:
nausea
'sickness' is the definition.
('nausea' can be a synonym of 'sickness')
'a value in north america' is the wordplay.
'value' becomes 'use' (I've seen this before).
'in' indicates putting letters inside.
'north america' becomes 'na'.
'a'+'use'='ause'
'ause' put within 'na' is 'NAUSEA'.
'that's' is the link.
(Other definitions for nausea that I've seen before include "Sick feeling" , "Feeling of revulsion" , "Feeling of sickness or disgust" , "Aversion" , "Malady" .)