Can I use a Tubular tyre in a Clincher rim?
Would you try to use glue on all 4 layers + tubular, some special tape or change rim ?


Change rim

The more layers of tape and glue you introduce the less firm the tire is attached and the more weight you add to your wheel. You want your tire firmly affixed to your rim for turning, braking, acceleration (on a rear wheel) performance. 


  No surprise seller told me it is possible...


Sellers say lots of things are possible.
Possible does not mean "safe", "performs well", "is recommended", "is best" etc.
Sometimes sellers do not have your best interests at heart.

It is also possible to use and angle grinder to cut down the walls of the rim. Then you would need less tape. Please don't do that. But, if you do we'd like video.