Where varnish goes immediately (2,3,4)
I believe the answer is:
on the nail
'immediately' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for on the nail that I've seen before include "Where varnish is put" , "Prompt" , "Where a coat may be hung" , "Exact" , "Promptly" .)