Fabric join (4)
I believe the answer is:
seam
'fabric join' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for seam that I've seen before include "Joint between two edges" , "Line of sewing - stratum of coal" , "Unfasten" , "Fabric join" , "The line where two edges are stitched together" .)