Reference compiler exposing nonsense about good English (5)
I believe the answer is:
roget
'reference compiler' is the definition.
(thesaurus compiler Peter Mark Roget)
'exposing nonsense about good english' is the subsidiary indication.
'exposing' means one lot of letters goes inside another (expose can mean to open up).
'nonsense' becomes 'rot' (I've seen this before**).
'about' indicates putting letters inside.
'good' becomes 'g' (abbreviation).
'english' becomes 'e' (abbreviation).
'rot' going around 'g' is 'rogt'.
'rogt' going around 'e' is 'roget'.
(Other definitions for roget that I've seen before include "Scholar remembered for his Thesaurus" , "Thesaurus inventor" , "From bookmaker" , "lexicographer" , "English doctor, compiler of a thesaurus, d. 1869" .)