comic vs top banana

comic and top banana both are nouns.

Word	Noun	Adjective	Verb	Adverb
comic	Yes	Yes	No	No
top banana	Yes	No	No	No

As nouns, top banana is a hyponym of comic; that is, top banana is a word with a more specific, narrower meaning than comic:

comic (noun)	top banana (noun)
a professional performer who tells jokes and performs comical acts	the leading comedian in a burlesque show
	the most important person in a group or undertaking

comic (adjective)	top banana (adjective)
of or relating to or characteristic of comedy
arousing or provoking laughter