Deleting photos from photo stream on an iphone

Open the my photo stream album in the grid view, tap Select, tap the photos you want to delete then tap the trash icon. Just be aware that this will delete them from iCloud and all devices/computers that are signed into your photo stream.

What about Icloud photos on a phone when i select it there is no trash option.

The only photos that do not give you the option to delete are photos that were synced to your device from a computer using iTunes. These photos can only be removed by deselecing them on the Photos tab of your iTunes sync settings and syncing.