Writer had visor and mask lifted now and again to deliver some vernacularisms (6)
I believe the answer is:
idioms
'some vernacularisms' is the definition.
(vernacularisms are idiomatic language)
I don't understand the remainder of the clue.
(Other definitions for idioms that I've seen before include "Dialectic words" , "Group of words having a meaning not obvious from the words e.g over the moon" , "Modes of expression peculiar to a language" , "styles of speech" , "Expressions" .)