Proletariat accepting start of Latin’s polite comment (10)
I believe the answer is:
'polite comment' is the definition.
(pleasantries are polite comments)
'proletariat accepting start of latin's' is the wordplay.
'proletariat' becomes 'peasantry' (proletariat means the worker class).
'accepting' indicates putting letters inside (inserted letters are accepted).
'start of' says to take the initial letters.
The first letter of 'latins' is 'l'.
'peasantry' placed around 'l' is 'PLEASANTRY'.
(Other definitions for pleasantry that I've seen before include "Jocular comment" , "An agreeable remark" , "Slightly amusing remark" , "Joke, banter" , "Polite remark" .)