None sit out showing stress (7)
I believe the answer is:
tension
'stress' is the definition.
(synonyms)
'none sit out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'none'+'sit'='nonesit'
'nonesit' is an anagram of 'TENSION'.
'showing' acts as a link.
(Other definitions for tension that I've seen before include "anxious state" , "Strain, nervousness" , "Uneasiness" , "Strained condition" , "One isn't (anag.)" .)