Clídna

In Old Irish, a D anywhere but at the beginning of a word or after an L, N, R, was pronounced like TH in 'they'. Cleedhna. It wasn't until later on, possibly Middle Irish or Classical Gaelic when they started using the _ponc séimhithe_ (the dot over a consonant) to indicate lenition. In the Old Irish period, T was pronounced D (anywhere but where I've indicated), and TT was pronounced T.

Clídna is pronounced: Klee-na.