Some types do such as my Clematis 'Comtesse de Bouchaud' and C Victoria. I cut theses back to the ground after flowering.
If you dont have the types that turn brown at the bottom is it wilt?

I don't know Drc if it's wilt as not had this before.

Wilt looks like wilt in one or more stems so I think you would spot that. Brownness at the bottom is normal in certain types of clematis at around this time of year. Why not put a photo and the name on here and we can then be sure. Do you have any Clematis viticella? My viticella Madame Julia Correvon goes brown at the bottom every year.

Drc. I don't have Clematis Vitcella I shall try to take photos tomorrow.

I generally expect the bottom ones to go brown and this year it's ever more noticeable, I've been blaming the dry weather and the hot temperatures.

Sorry I assumed you meant just at the bottom. Lets look at the photos tomorrow mine go brown sometimes when short of Magnesium and I give them Epsom salts.