The first part of your question raises an issue with the term “propaganda”. I thought you needed help translating it into Arabic, until I read the second part, where the issue seems to be more related to the Arabic term DA"IYA. I hope I grasped what you need. If you feel I have not addressed it, please let me know, and accept my apology.

1. Missionary: In the minds of many people, the term “missionary” is often associated with Christian missionaries, but I think there is no need for this exclusive association. Anyone who preaches a religion is a missionary.

Also, many people think of missionaries as globetrotters, roaming the continents and going to the remotest areas to carry their faith to all of God’s children. The truth is that the mission of missionaries is to carry their faith to whoever will listen, even to their own communities.

2. Preacher: The term “preacher” is likewise unfairly delimited by many people who think of preachers as orators and homilists. In fact, to preach is to advocate the life of faith and virtue but whatever means.

3. Advocate: Advocacy is a broader concept, and the term "advocate" can be appropriate in some contexts.

Fuad

Tarweej ("a" is accented): Propaganda.

De-aaya ("e" and last "a" accented): Implies propaganda but can also mean an ad (ala TV ad). It can also mean notice and announcement.

Though they have the same root verb, these are two different words:
1- Al-Daai'ya: (الداعية) The Muslim missionary, (The plural is دُعاة Du'aat).

2- Al-Di'aaya: (الدعاية) Propaganda (The plural is دعايات Di'aayat).

The root verb for both is دعا (Da'aa), meaning "call". And those who call for Islam or for God are called Du'aat, literally "callers". The nearest meaning for the word is "missionary", but in an Islamic sense. It's particularly used to describe those who are sent to promote Islam among non Muslims. Then it started to be used to describe any prominent Muslim scholar.

The second word (Di'aaya) means "propaganda", and in some areas it's colloquially used to mean "Advertisement" or, more specifically, "a TV commercial".

You may feel that some scholars get involved in some propaganda, but this is NOT what gives them their name!

This is my suggestion about what to call a cleric who acts as a 'daa'ya' to give an opinion regarading the propagation of Islam.

Or
A propagation Muslim Cleric/Scholar
or
Islamic propagation cleric/scholar:

are other suggestions where 'propagation' is frequently used as a term to denote the دعاية 'de'aaya' for Islam.

HTH

Waa'iTH = the person who provide exhortation.
Wa'TH = exhortation.

Could this is what you have in mind?

As a matter of fact I still am not 100% clear of what you're trying to say in your added note and in particular:
"which relates to the more general sense of persuasion and exhortation, is what I was looking for. "

HTH