Isn't one affected with stress? (7)
I believe the answer is:
tension
'stress?' is the definition.
(I know that stress can be written as tension)
'isn't one affected' is the wordplay.
'affected' indicates an anagram.
'isnt'+'one'='isntone'
'isntone' anagrammed gives 'TENSION'.
'with' acts as a link.
(Other definitions for tension that I've seen before include "Assay" , "State of strain or suspense" , "A pulling strain" , "anxious state" , "Nervous strain" .)