Have side mended with glue (8)
I believe the answer is:
adhesive
'glue' is the definition.
(I've seen this in another clue)
'have side mended' is the wordplay.
'mended' indicates anagramming the letters.
'have'+'side'='haveside'
'haveside' is an anagram of 'ADHESIVE'.
'with' is the link.
(Other definitions for adhesive that I've seen before include "Tending to stick" , "doing some bonding" , "It sticks things together" , "Stuff that sticks" , "Substance that sticks" .)