set in
• (of something unpleasant or unwelcome) begin and seem likely to continue.
• "tables should be treated with preservative before the bad weather sets in"
• insert a part such as a sleeve into a garment.
• "with a properly drafted pattern you can often set the sleeve in without adding an easing stitch"
set-in
adjective
• (of a sleeve) made separately and inset into a garment.
