If subleasing is disallowed under my leasing agreement, can I still?
Yes. What you describe would not be a violation of a typical lease provision against subleasing. You are simply giving another party permission to use a desk that you are not using in your leased offices. That is not subleasing under any definition. Moreover, by "rent out a desk" what you are actually "renting" is not real property but rather you are simply granting a license of use for furniture that you presumably own, and the space incidental to that use. However you must be careful that the person using the "desk" (your licensee) does not exhibit conduct that can be construed as having a leasehold interest in your space. This would include placing a separate name on the door or lobby directory, receiving mail at the premises, independent use of building services or employees, or any other conduct consistent with having an independent leasehold interest in the space. In addition, if you did wish to sublet space, a prohibition against subleasing does not preclude you from requesting an amendment to your lease which would allow you to sublease. A lease can always be modified, changed or amended if the parties are agreeable and/or sufficiently motivated to change it.