Note first of threads in needlework (8)
I believe the answer is:
crotchet
'note' is the definition.
(musical note)
'first of threads in needlework' is the wordplay.
'first of threads' becomes 't' (1st letter of 'threads').
'in' is an insertion indicator.
'needlework' becomes 'crochet' (crochet is a kind of needlework).
't' inserted inside 'crochet' is 'CROTCHET'.
(Other definitions for crotchet that I've seen before include "In music, it has quarter the time value of a whole note" , "Two quavers as one note" , "as mark scored" , "Peacock's castle" , "Fancy" .)