I've solved 7 across okay, but I don't really get why the last two letters are OD. Something to do with overdose, or a current slang term I've not come across maybe?
Hi WildAbout Words & welcome to AB :-) It's always nice to post the full clue, so that people without the puzzle can more readily help - 7a Religious assembly to hear evil act, party's over (5) Synod - "sin" (evil act, heard) + 'do' (party, over)