fun vs clowning

fun and clowning both are nouns.

Word	Noun	Adjective	Verb	Adverb
fun	Yes	No	No	No
clowning	Yes	No	No	No

As nouns, clowning is a hyponym of fun; that is, clowning is a word with a more specific, narrower meaning than fun:

fun: verbal wit or mockery (often at another's expense but not to be taken seriously)
clowning: a comic incident or series of incidents

fun (noun)	clowning (noun)
activities that are enjoyable or amusing	acting like a clown or buffoon
violent and excited activity	a comic incident or series of incidents
a disposition to find (or make) causes for amusement
verbal wit or mockery (often at another's expense but not to be taken seriously)