That story about an abstainer is mere gossip (6)
I believe the answer is:
tattle
'mere gossip' is the definition.
'tattle' can be an answer for 'gossip' (I've seen this before). I am not sure about the 'mere' bit.
'that story about an abstainer' is the wordplay.
'that story' becomes 'tale' (synonyms).
'about' means one lot of letters goes inside another.
'an abstainer' becomes 'TT' (short for teetotaller, someone who avoids alcohol).
'tale' placed around 'tt' is 'TATTLE'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for tattle that I've seen before include "Inform on someone" , "Tell tales" , "Chatter idly" , "Divulge secrets" , "'Gossip, idle talk (6)'" .)