What version of Premiere Elements and on what computer operating system is it running?
What workspace are you working in - Expert or Quick if Premiere Elements 11, 12, or 13 or Timeline Sceneline if Premiere Elements 10 or earlier?
Is the Soundtrack in the open configuration? Where is this area of the Soundtrack content that you want to remove - in the middle, at the very end, or elsewhere?
How are you trying to delete what you do not want? And, what happens when you try - besides the part not deleting.
Please review, consider, and supply more information.
Any questions or need clarification on any of the above, please do not hesitate to ask.