They have an interest in conversion schemes (12)
I believe the answer is:
missionaries
This clue could be a double definition.
'they' is the first definition.
Both the definition and answer are plural nouns.
Maybe they are linked in a way I don't understand?
'an interest in conversion schemes' is the second definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'have' is the link.
Can you help me to learn more?
(Another definition for missionaries that I've seen is " ministers sent abroad".)