I have several issues with this one. 1) "～십시오" is a very polite ending, so it strongly implies "please + verb" in English. 2) "Clean up" is more accurate and natural. Cleaning is in general, cleaning up is to complete a specific task. 3) Finally, "leaves" should be accepted for 낙엽. If you are cleaning them up, OF COURSE they are on the ground, they are fallen. Saying fallen leaves is redundant and we native speakers absolutely don't say "fallen". We're not going to clean up the leaves that are still on the trees. Hopefully, this answer will get "fixed up" soon!!
In English I would say "clean up" instead of clean. A more precise English translation would be either rake or rake up.
...십시오 is a polite request form, and please is implied. That should be included in the translation.
As others have said, it really should be "clean up" instead of just "clean." Cleaning leaves gives the impression of washing every leaf. I did flag it, but we'll see.
Is it wrong to use the word "please" in the English translation here?