The mantle of sleep is disturbed (7)
I believe the answer is:
pelisse
'the mantle' is the definition.
(pelisse is a kind of mantle)
'sleep is disturbed' is the wordplay.
'disturbed' indicates anagramming the letters.
'sleep'+'is'='sleepis'
'sleepis' with letters rearranged gives 'PELISSE'.
'of' acts as a link.
(Other definitions for pelisse that I've seen before include "In a military cloak" , "Long cloak" , "one worn by lady" , "coat" , "Sleeveless cape" .)