Well versed describes a poet or reader who has a strong working knowledge of verse, meter, rhyme, and other poetic conventions. It can also mean being widely read in poetry, but the phrase usually points to familiarity with how poems are made and how they work.
Example
She was well versed in sonnets, so she heard the steady beat in each line:
When winter came, the apple trees stood bare
and kept their dark advice against the sky.