Soft quilt (9)
I believe the answer is:
eiderdown
'soft quilt' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for eiderdown that I've seen before include "Feather quilt" , "I wondered about this warm bed covering" , "what keeps retired people warm" , "thermal insulation" , "What might keep one warm" .)