Clear is original so making the call clear or tinted is entirely up to you. The original supplier had theirs branded as TripleX. They were used pretty much across the Triumph line, the various BMC lines and most other British cars. However....
I know there has been a problem with some of the TripleX windshields as of late. They are a bit too tall and the curvature is off. I had lunch the other day with some guys that meet up at a local British car shop and we were looking at a couple windshields that had cracked on install as well as a couple of others that had not been installed, comparing them to the pitted one that came off a car. It was obvious that they were not to spec. They had two or three TR6s sitting around the shop waiting for a windshield and were talking with the customers to see if they wanted to try another parts source out of the UK and hope for better luck or go aftermarket. The same windshield is used across the TR4 through 6 as well as the earlier Spitfire and GT6 models. At this point it looks like aftermarket is the way to go if you must do it now. If you want to hold out for the OE supplier, you will either need to wait until they get their act together and start supplying properly made windshields, try and find some NOS or see what the UK suppliers have to say.