Hi George,
this should to the job:
#popclip
name: Cloze
icon: monospaced {{
javascript: popclip.pasteText('{{c1::' + popclip.input.text + '}}')
description: Adds cloze deletion to selection
(The above block is an extension snippet – select it to install the extension with PopClip)
You can choose any name, description or icon you like, as detailed in the documentation. I just named it Cloze, as it looks you are a fellow Anki user 