Spool for winding yarn (6)
I believe the answer is:
bobbin
'spool for winding yarn' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bobbin that I've seen before include "Reel, spool" , "Reel for yarn" , "Spool for thread or yarn" , "Cylinder for winding thread" , "Small spool holding thread in machine" .)