Can the device hold the clip only? I am worried that the device will fall off.

The clip holds the clothes firmly and powerfully in place.
The receiver itself is held by underwear, etc., so it is unlikely to fall off.
It is recommended that you wear tight-fitting briefs-type or trunks-type underwear.
If you are concerned about the stability of the clip, you can use an optional garter or supporter.

■Product details
Men’s wearable urine collector AS-URI S/M/L size
https://asahi-packaging.com/products/mr-urinar/