Jeans joint (4)
I believe the answer is:
seam
'jeans joint' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for seam that I've seen before include "Join in knitted garment" , "Join in material - layer of coal" , "Stratum (of a mineral)" , "Unfasten" , "Join - thin layer" .)