Well, I find it easiest to quote Wikipedia:
A clerihew is a whimsical, four-line biographical poem invented by Edmund Clerihew Bentley. The first line is the name of the poem’s subject, usually a famous person put in an absurd light, or revealing something unknown or spurious about them. The rhyme scheme is AABB, and the rhymes are often forced. Wikipedia
I should add that the meter is rather informal.
I subscribe to Scientific American. Recently the renewed a practice of including a page of poetry in their magazine. Seems weird to me, but so far the poems have been pretty much science oriented, so they fit, even if the practice feels funny to me. Their Clerihew page has been littering my desk for a couple months now, and I’m finally getting around to posting about it.
So I challenge you to write a Clerihew and post it. Here’s one off the top of my head:
Rogers George writes Writing Rag
At first he thought it’d be a gag
But comics and grammar go together,
So he wrote a post and then another.