clear

Boy WB, that's a knotty one. It might make more sense with "in the presentation." However I 'd write

In the (or "my") presentation if there is anything he is not clear about, please tell him to feel free to contact me

You need a word like 'in' or 'concerning' or a phrase like 'relating to' to join 'clear about' and 'the presentation'.

If there is anything he is not clear about in/concerning/relating to the presentation, please tell him to feel free to contact me.

If you rearrange the sentence it may be clearer:

If there is anything in/concerning/relating to the presentation [that] he is not clear about, please tell him to feel free to contact me.

Excellent answers. Thank you.

Why thank you, you're quite welcome WB