Tense, but succeeded replacing fine stitching (6)
I believe the answer is:
suture
'stitching' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for suture that I've seen before include "Medical stitch" , "Surgical thread, seam" , "Stitch for 31ac" , "Material for sewing a wound" , "Thread used by surgeons" .)