Protection member gets for a Congressional event? (6)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

[Edited:] I think the intention here is M (abbreviation for member, as in MP = Member of Parliament) after CON (abbreviation for Congressional?) + DO (slang for a party = event). I couldn’t find dictionary backing for this meaning of CON as an abbreviation, though Flea @1 has found some evidence.  I’m also not sure why M is at the end: perhaps we’re supposed to take “protection” as meaning the rest of the wordplay is above, but that seems a bit too devious. Extended definition: protection for the male member during sexual congress.