Used in a sewing machine it goes round a screw (6)
I believe the answer is:
thread
'it goes round a screw' is the definition.
The definition suggests a singular noun which matches the answer.
'used in a sewing machine' is the wordplay.
'used in' indicates the central letters (the letters used on the inside of the word).
'a sewing' becomes 'gather' (gather is a kind of sewing).
'machine' becomes 'read' (I am not sure about this - if you are sure you should believe this answer much more).
The middle of 'gather' is 'th'.
'th'+'read'='THREAD'
Can you help me to learn more?
(Other definitions for thread that I've seen before include "Strand, cord" , "Prominent spiral part of a screw" , "clothes casually cut" , "Yarn, string" , "Dearth of stitching material" .)