I suspect you have hit return at the end of each line in your poem and so HubPages is "starting a new Paragraph" each time and so inserting a blank line. However, I don't know how you can format it without using the return key. I don't think they have an html option in the layout. But if other people's poetry looks OK then there must obviously be a way to do it. It might be as well to ask the question in the forums.
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