white elephant vs possession

white elephant and possession both are nouns.

Word	Noun	Adjective	Verb	Adverb
white elephant	Yes	No	No	No
possession	Yes	No	No	No

As nouns, possession is a hypernym of white elephant; that is, possession is a word with a broader meaning than white elephant:

white elephant (noun)	possession (noun)
albinic Indian elephant; rare and sometimes venerated in east Asia	anything owned or possessed
a valuable possession whose upkeep is excessively expensive	the act of having and controlling property
	(sport) the act of controlling the ball (or puck)
	the trait of resolutely controlling your own behavior
	a territory that is controlled by a ruling state
	a mania restricted to one thing or idea
	being controlled by passion or the supernatural