He's a Poet who Don't Know It.

[Brownlie]

He's a Poet Who Don't Know It (Free-ranging allowed, creative comments appreciated)

He's a poet who don't know it; -- I would avoid using a cliché for the title and first line. I think you can get away with bad grammar if you're imitating a way some people speak, but I'm not so sure here.
it's not of relevance to him,
his pride he thinks to stature win. --To stature win is awkward. I would never cheat to achieve meter. Always try and make it sound natural.
He seeks a mentor to guide his place
to please his clique, promote his face. -- Whenever you insert A rhyme scheme of AA it will be harder for people to take your work seriously.
His mind profound but lacking liberty, -- You seem to have omitted some crucial words that would hold up the sentence structure.

possessed to win applause and flattery.
On stage he plied the written words of art, -- written words of art is incredibly abstract, and thus somewhat meaningless. The more specific the more the reader knows what's going on.

divided from his self part; a broken heart
that questions, is he now upon the stage,
or words and heart in life engaged?

For he's a poet who don't know it.
He seeks to best the common place.
His aging ass would like to grace
a comfy padded rocking chair;
with, what else, poetic flair.
For one with practiced wits as he
who casts his nets with subtlety
and care; he tires then ascends the stair
and breathless falls upon a chair;
with age, though aspirations debonair. -- Debonair sounds incredibly forced, because you use simple language and then this pops up out of the blue. Plus, it is kind of a strange word. At least, that's how I see it.

Should he grasp the naked phantom there
and be the poet, and in his glory
smile to know it?

Still, it's buried in his heart apart,
and though it sings within his head;
he has no ear to hear, but fears to know it.
Yet, he is on fire within, of life's desires;
but seeking safety he conspires
to trample out those restless fires.
With all of everything, his age to doubt,
the decades growing thin without;
despite what dims the outer rim,
his secret treasure hides within, and sadly
still, he's a poet who don't know it.

Ok I like you and left you some notes. I'd like to see something a little more real from you, but people do like different things.