Record nothing! Two unknowns making a resin (5)
I believe the answer is:
epoxy
'a resin' is the definition.
(epoxy is a kind of resin)
'record nothing two unknowns' is the wordplay.
'two unknowns' can mean two replacements for 'unknown'.
'record' becomes 'ep' (abbreviation for extended play record).
'nothing' becomes 'o' (looks like zero - 0).
'unknown' becomes 'x' (algebra).
'unknown' becomes 'y' (algebra).
'ep'+'o'+'x'+'y'='EPOXY'
'making' acts as a link.
(Other definitions for epoxy that I've seen before include "Synthetic polymer used in adhesives, paints, etc" , "Hard-setting resin" , "Type of resin" , "Synthetic adhesive, paint etc." , "Adhesive; plastic" .)