Expose yourself to the mafia in brief public assembly (5,3)
I believe the answer is:
flash mob
'the mafia in brief public assembly' is the definition.
I can't judge whether this defines the answer.
'expose yourself' is the wordplay.
'expose' becomes 'flash' (flashing is a kind of exposing).
'yourself' becomes 'mob' (I can't justify this - if you can you should believe this answer much more).
'flash'+'mob'='FLASH MOB'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for flash mob that I've seen before include "streakers?" , "Ad hoc group assembled to do something unusual in a public place" , "Sudden mass of people" , "Unexpected gathering" .)