how can I remove an object from a scene

It depends.

Is the camera static during the shot? If the camera is moving, or zooming - it is going to be very complicated to remove.

Is the object unobscured by other objects passing in front of it during the entire scene?

You might post a screen shot of the scene and point out the object you wish to remove to get better advice.

MtD

Park the playhead of the timeline on a frame of the scene you want to fix.

Export a single frame of the clip by going to the menu File > Export > Using Quicktime Conversion . . .

Choose Still Image for the Format, then Save it.

Open that image in Photoshop and use the clone tool to hide the problem.

Import the fixed still back in FCP, and edit it on to a video track directly above the clip in the timeline you want to fix.

Double click on the image on the timeline to load it to the viewer, in the viewer click on the Motion Tab, and use the crops settings to restrict the retouched frame to just the area you want to cover.

MtD

Is there a portion of the shot you can move over it to cover it?

Can you just blur it out?

If you would post a screen shot of what you are trying to fix it will help immensely.

MtD

You might take a lock at Pixelmator, as an affordable alternative to PS. It too offers the clone stamp tool that MtD recommended.

Russ