Foolish and irrelevant talk (7)
I believe the answer is:
blather
'foolish and irrelevant talk' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for blather that I've seen before include "(Talk) gibberish" , "Foolish and irrelevant talk" , "Rubbishy old talk, foolish chat" , "Foolish chatter, just oul' talk" , "Long-winded talk making little sense" .)