Salesman born in Idaho felt discontent (7)
I believe the answer is:
repined
'felt discontent' is the definition.
(to repine is to feel sad)
'salesman born in idaho' is the wordplay.
'salesman' becomes 'rep' (I've seen this before).
'born' becomes 'ne' ('born' in French - used to indicate a birth name).
'in' is an insertion indicator.
'idaho' becomes 'ID' (abbreviation).
'ne' placed inside 'id' is 'ined'.
'rep'+'ined'='REPINED'
(Other definitions for repined that I've seen before include "Languished" , "Grudged" , "Was not happy" , "Expressed discontent" , "Fretted; was discontented" .)