You can trim the video without getting any other apps, just tap the screen during playback to see the edit controls.
For more info, check out the iPad User Guide
You can trim the frames from the beginning and end of a video that you just recorded, or from any other video in your Camera Roll album. You can replace the original video, or save the trimmed version as a new video clip.
Trim a video: While viewing a video, tap the screen to display the controls. Drag either end of the frame viewer at the top of the video, then tap Trim.
Important: If you choose Trim Original, the trimmed frames are permanently deleted from the original video. If you choose “Save as New Clip,” a new trimmed video clip is saved in your Camera Roll album, leaving the original video unaffected.