In Ecclesiatical Latin, the way preferred by the Church (more Romano), it would be lec-tsee-o
Like the ci in Spanish nacional, or the zi it Nazi
The "ti" is a syllable. So not leks-io but lec-tsee-o. Three syllables. One for each vowel
We can see this is how it was pronounced in the history of the Church if you look at Latin writings that aren't heavily edited...they often will spell words inconsistently, and according to pronunciation. Hence instead of caelum you will see celum, I good indicator that at that time and place æ and e were already said the same. And you will see sometimes "cio" instead of "tio" in more Germanic regions. The Germans had this habit of pronouncing ci, or ce, rather than chee, or che, (Ch as in Church) as "tsee" or "tse"
Reason is by study, labor, and exercise of logic, philosophy, and other liberal arts corroborated and quickened; and the judgment both in them and also in orators, laws, and stories much ripened. And although poets are with many men taken but for painted words, yet do they much help the judgment, and make a man among other things well furnished in one special thing, without which all learning is half lame…a good mother wit.- St. Thomas More