Thin cotton fabric (11)
(Other definitions for muslin that I've seen before include "Lightweight cotton cloth" , "dress material" , "Light cotton cloth" , "Lightweight cotton fabric" , "Fine soft plain-woven cotton fabric of gauzy appearance" .)
'thin cotton fabric' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cheesecloth that I've seen before include "flimsy material" , "Loose-woven cotton fabric" , "Loosely woven material" , "Loosely woven cotton fabric" , "Light woven fabric for protecting food or making shirts" .)
(Other definitions for seersucker that I've seen before include "Cotton" , "Puckered fabric" , "Material" .)