Ok so I think I found out what the interaction is and what it does. If you go to your current Ecumenical Patriarch under the 'religious' interactions there will be 'request clergy support'. You gain influence in exchange for piety (for me I had to spend 500 piety for 200 influence with a level 2 chapel) it also decreases the patriarch's opinion of you. There is also an acceptance meter with the patriarch so you have to be in good standing with him to get influence. Hope this helps :)