AT a dinner party at a Peak residence last night the conversation (a better class of socialite this, you understand) drifted towards the just concluded talks between US President Bill Clinton and his beleaguered Russian counterpart Boris Yeltsin in Vancouver. ''Of course, Yeltsin has everything to play for,'' regaled one of the diners, pausing momentarily to fill his wineglass. ''If he loses the current power struggle he'll have to face the terrible consequences.'' ''And what would that entail?'' inquired a gentle female voice from the other end of the table. ''Yeltsin will be dragged through the streets by the Bolsheviks, that's what,'' he shot back. Ouch!