Japan? Go around mid-April (7)
I believe the answer is:
varnish
'japan?' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for varnish that I've seen before include "Glossy stain" , "Glossy coat" , "Protective coating" , "Wood or nail coating" , "Shiny transparent coating used on wood" .)