One isn't agitated in anxiety (7)
I believe the answer is:
tension
'anxiety' is the definition.
(I've seen this before)
'one isn't agitated' is the wordplay.
'agitated' indicates an anagram.
'one'+'isnt'='oneisnt'
'oneisnt' with letters rearranged gives 'TENSION'.
'in' is the link.
(Other definitions for tension that I've seen before include "anxious state" , "Conflict" , "The effect of force exerted in or on something" , "Strain, nervousness" , "Mental or emotional strain" .)