Hi aceritch,
I'm sorry to hear you are having issues with your iPhone. I also apologize, I'm a bit unclear exactly what you are seeing when you try to send your video clip, or if this is happening with any other messages (other video clips, pics, audio, text, etc). If you continue to have issues sending video in Messages on your iPhone, you may find the information and troubleshooting steps outlined in the following articles helpful:
Send audio, photos, and videos using Messages on your iPhone, iPad, or iPod touch with iOS 8 - Apple Support
iOS: Troubleshooting Messages - Apple Support
Regards,
- Brenden