Answer:
Easy to talk with.
Step-by-step explanation:
The word 'effable" means someone who is easy to approach, easy to talk to and open. It signifies someone who is not irritated or annoyed by others approaching him/ her.
From the given passage, the speaker of the passage narrates how he managed to get to talk to Uncle Charles. Despite having a lot of questions and wondering whether he's being a nuisance to the other person, he then realized that Charles didn't mind at all. Added to that, the speaker admits he himself is shy so was a bit reserved to approach someone he hardly knew. But all of his reservations were swept away when he realized that the old man was "quite effable", making their conversation easy and relaxed.