Sealant placed on borders of tapestry (5)
I believe the answer is:
putty
'sealant' is the definition.
(I know that putty is a oil putty)
'placed on borders of tapestry' is the wordplay.
'placed' becomes 'put' (I've seen this before).
'on' means one lot of letters go next to another.
'borders of' means to remove the middle letters.
'tapestry' with its middle taken out is 'ty'.
'put'+'ty'='PUTTY'
(Other definitions for putty that I've seen before include "Window-sealing paste" , "Window glass sealant" , "Malleable form of glas holder" , "Window fixer" , "Glazier's paste" .)