Unruffled Sumatran quilt stuffing (8)
I believe the answer is:
tranquil
'unruffled' is the definition.
(I know that unruffled can be written as tranquil)
'sumatran quilt stuffing' is the wordplay.
'stuffing' indicates a hidden word.
'TRANQUIL' can be found hidden inside 'sumatran quilt'.
(Other definitions for tranquil that I've seen before include "Restful" , "Peaceful - calm" , "Peaceful and serene" , "Free from disturbance" , "not making waves" .)