Non-drinkers receive insignificant comments online (6)
I believe the answer is:
tweets
'comments online' is the definition.
'non-drinkers receive insignificant' is the wordplay.
'non-drinkers' becomes 'tts' (I can't justify this - if you can you should give a lot more credence to this answer).
'receive' means one lot of letters goes inside another.
'insignificant' becomes 'wee'.
'tts' enclosing 'wee' is 'TWEETS'.
(Other definitions for tweets that I've seen before include "Posts made on Twitter" , "Sends social media comments, information, etc" , "online comments" , "Chirps social media postings" , "Social media messages" .)