Lectures about last weekend's mischief (5)
I believe the answer is:
talks
'lectures' is the definition.
('talk' can be a synonym of 'lecture')
'last weekend's mischief' is the wordplay.
'weekend' becomes 'k' (I've seen this in other clues).
'mischief' indicates an anagram.
'last'+'k'='lastk'
'lastk' is an anagram of 'TALKS'.
'about' acts as a link.
(Other definitions for talks that I've seen before include "negotiation" , "Speaks" , "Verbalises" , "Chats; lectures" , "negotiations" .)