Narrow piece laid into long cloth (9)
I believe the answer is:
pinstripe
'cloth' is the definition.
(I know that pinstripe is a type of cloth)
'narrow piece laid into long' is the wordplay.
'narrow piece' becomes 'strip' (as in a strip of material or land).
'laid into' is an insertion indicator.
'long' becomes 'pine' (to pine for someone is to long for them).
'strip' put into 'pine' is 'PINSTRIPE'.
(Other definitions for pinstripe that I've seen before include "Fabric - insert pip (anag)" , "business suit" , "maybe a suit" , "Cloth for making suits" , "material" .)