Stress? One isn't affected (7)
I believe the answer is:
tension
'stress?' is the definition.
('tension' can be a synonym of 'stress')
'one isn't affected' is the wordplay.
'affected' indicates anagramming the letters.
'one'+'isnt'='oneisnt'
'oneisnt' with letters rearranged gives 'TENSION'.
(Other definitions for tension that I've seen before include "Uneasiness" , "Anxiety" , "anxious state" , "Intones (anag) - stress" , "Strained condition" .)