double-dealer vs slicker

double-dealer and slicker both are nouns.

Word	Noun	Adjective	Verb	Adverb
double-dealer	Yes	No	No	No
slicker	Yes	No	No	No

As nouns, slicker is a hypernym of double-dealer; that is, slicker is a word with a broader meaning than double-dealer:

Other hypernyms of double-dealer include beguiler, cheat, cheater, deceiver, trickster.

double-dealer (noun)	slicker (noun)
a person who says one thing and does another	a macintosh made from cotton fabric treated with oil and pigment to make it waterproof
	someone who leads you to believe something that is not true
	a person with good manners and stylish clothing