Many types of wood will absorb stain unevenly, especially pine and maple. A thin coat of blond shellac can help. It will lightly seal the wood, but not completely, and your stain can then be applied more evenly.
If going over the piece with a rag dampened with solvent doesn't solve the problem, sand it down, cut your shellac with a little methyl hydrate, apply a thin coat, and then try your stain. Better yet, do it on a sample first.