Lives outside court, initially undergoing stress (5)
I believe the answer is:
ictus
'stress' is the definition.
(thesaurus)
'lives outside court initially undergoing' is the wordplay.
'lives' becomes 'is' ('be' can be a synonym of 'live').
'outside' indicates putting letters inside.
'court' becomes 'ct'.
'initially' indicates taking the first letters.
The initial letter of 'undergoing' is 'u'.
'ct'+'u'='ctu'
'is' enclosing 'ctu' is 'ICTUS'.
(Other definitions for ictus that I've seen before include "Stroke" , "strokes" , "Seizure" , "recurrence of disease results" , ""fit"" .)