It takes a moment to place 'anchor' as something other then a awkward boat pun, which is a pretty simple example of Aradia's priorities, if you think about it. The phrase is dimly recognized from past conversations with Clara, and it's still an annoying blank spot in her growing understanding of ghostly life. But asking would be painfully rude, even by her usual standards, so the topic drops in favour of shameless gossip.

"It'd be nice to chat more often, but I don't want to be a hassle and drag you across the river without cause. Especially if your granddaughter's such a handful." Clara's lingering connection to her family is important, if somewhat baffling, and Aradia would hate to take time away from that. "Though it sounds like she's trying to have fun, not worry you, even if I'm sure she appreciates you looking out for her all the same."

Unspoken is the assumption that the elder ghost's oft-mentioned grandchild can see the dead. The alternative feels too depressing to pry into, despite being more likely.