Gown is now worn in fatigue (10)
I believe the answer is:
drowsiness
'fatigue' is the definition.
(thesaurus)
'gown is now worn in' is the wordplay.
'gown' becomes 'dress' (gown is a kind of dress).
'worn' indicates anagramming the letters (worn can mean damaged).
'in' indicates putting letters inside.
'is'+'now'='isnow'
'isnow' anagrammed gives 'owsin'.
'dress' placed around 'owsin' is 'DROWSINESS'.
(Other definitions for drowsiness that I've seen before include "Dozy feeling" , "Lethargy, somnolence" .)