Dirt and dust inside the drive - pretty normal for that age and use, in fact other than rust it's not all that dirty. Compressed air might do the job if the dirt is not "cigarette glaze" (sadly, if often is) or otherwise very sticky. Heads might need cleaning as well - I'd do it anyway, unless you've never cleaned anything fragile in your life, in which case maybe practise w IPA soaked Q-tips on something else first.
Stepper motor could use some more cleaning, as does the case - if you do this, clean the head afterwards (or clean them again) to prevent any loose dirt from migrating and destroying your floppies. If the stepper motor is not frozen it'll work. If rusty inside it'll wear itself out way faster but you can't do anything about that without total disassembly - and I do not recommend it if you don't have the skills and tools to realign the drive properly afterwards. See those two screws with blue paint that keep the stepper attached to the case? Do not remove those. The motor has to be in this exact spot, we are talking fractions of milimeter precision.
On this model there is a way to detach the floppy clamping arm without disturbing the upper head alignment but even that can cause it to sit somewhat crooked when reassembled, so if you don't know how to tell and how to fix that, don't remove that either. On the other hand I started reparing and cleaning floppy drives with this particular TEAC series so I know it well - if you are looking for a project rather then immediately working drive, you can take it all apart and make it shiny. You will need a scope and a good, pre-recorded 5.25" HD floppy to do the full mechanical calibration aferwards.
One more thing, if you clean the stepper you can apply a light coat of WD40 to it, do not spray directly, rather use a cloth or something (more Q-tips) to transfer the WD40. I do that sometimes, it tends to fill in the gaps between the metal plates that form the magnetic core and prevents further rusting due to moisture. Can be done 2 or 3 times if there is a lot of rust. One last thing, a lot of various "guides" to floppy drive repair pretty much tell you to dump grease everywehre - please don't do that. It will kinda work, for a year or two, then all the sticky grease will attract so much dirt it'll get worse than it is now, and be even harder to clean properly.