Try the very important and official Photo or video editing option on your iPhone/ iPad running on iOS 10/ iOS 9. This option also available in your old iOS 9 devices and New iOS 10 but marginally modification. Just go with simple steps for Trim video in iPhone 7 Plus/ iPhone 7 or other iPhone installed iOS 10. Some improved point also I discussed at here that may be very useful before you try it own self.
Before you go for trim your video finally, please keep one copy as a backup of your video at anywhere or online cloud app for Photos/ Videos.
Steps for Trim video in iPhone 7 Plus or iPhone 7: Remove selected part
1: Go to Photos app on your iPhone/ iPad.
2: Open it, See All saved videos and Easy to pick your one Tap on “Albums” from beneath tab.
3: Tap on Video That you want Trim, Next Tap on Blue Setting/ Edit icon at bottom.
4: Now, you need to drag video boundary line (Arrow mark) on Preview pan See below image.
Before finally save it, Play portion of video by tap on play button then Tap on Done.
Next, Your new trimmed video save in to another copy in same photos app.
Extra Dose: Before start Trim video you have an option for edit video to other apps, like iMovie. To Use this tap on Circle with Three dot inside icon. As we know iMovie is a pro feature editing tools for Give another sound from music app, Text on video, Change video contrast/ Brightness.
Steps Trim/ Cut Video in iOS 9: Open video on Screen > Top right corner tap on Edit > Slide video frame limits by dragging it > Then Done.
From Two option, Save as a New Clip | Trim Original