It may be concealed by varnishing edge (5)
I believe the answer is:
hinge
'it may' is the definition.
The definition suggests a singular noun which matches the answer.
'concealed by varnishing edge' is the wordplay.
'concealed by' indicates the answer is hidden within the clue.
'HINGE' can be found hidden inside 'varnishing edge'.
'be' is the link.
Can you help me to learn more?
(Other definitions for hinge that I've seen before include "On what a door swings" , "Joint on which something turns" , "Fastening for door etc" , "Moving joint" , "hang" .)