Decorative strip in knitting pattern starts to bulge on needles (6)
I believe the answer is:
ribbon
'decorative strip' is the definition.
(I've seen this before)
'knitting pattern starts to bulge on needles' is the wordplay.
'knitting pattern' becomes 'rib' (I've seen this before).
'starts to' suggests taking the first letters.
The first letters of 'bulge on needles' is 'bon'.
'rib'+'bon'='RIBBON'
'in' acts as a link.
(Other definitions for ribbon that I've seen before include "Long strip of material" , "Streamer" , "Thin strip of cloth" , "Narrow strip of coloured cloth, worn as ornament" , "Long, narrow band" .)