noun , an 'elvis' is a joint that has either been badly constructed or attended to.. resulting in prominent 'Sideburns' (i.e. uneven burning on one side during smoking), hence the musical reference.
Much debate rages on the subject of rescuing an Elvis, with the potential waste of cannaboids being a particularly thorny issue
Heard in after party conversation ; 'Sorry mate, its a bit of an 'Elvis', but i'm too wasted man!.. here, take the lighter'