He calls out for varnish (7)
I believe the answer is:
shellac
'varnish' is the definition.
(shellac is a kind of varnish)
'he calls out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'he'+'calls'='hecalls'
'hecalls' anagrammed gives 'SHELLAC'.
'for' is the link.
(Other definitions for shellac that I've seen before include "Resin in flakes, used to making varnish" , "Take a shine to" , "coat" , "Varnish ingredient" , "(it's in old records)" .)