Periodically I see kanji that don’t have the reading in wanikani. I asked a friend if this was a special reading and she said no, but for the word 賭博 the reading is と.ばく。 Wanikani only has か、for this kunyomi for “gamble”.
Is this a special reading? Any reason why it wouldn’t be on WK, even on the entry page?
Just email them about it, they’ll add it. They make updates all the time. Presumably just slipped through the cracks since no words that use it are taught, so they haven’t had anyone try to enter it and fail yet, which is usually how these things are caught.
Also, just to let you know, there are many resources where you can check the readings for kanji. If you’re concerned about the reliability of things like Jisho or Wiktionary, you can go to something like Kanjipedia. I know that one sounds just as iffy as the others, but it’s actually run by the people who do the Kanken exams.