The phrase "bone to pick" is commonly used to refer to a topic or issue that someone is upset about and wants to discuss or argue about it. If you're looking for synonyms for "bone to pick," you might consider these alternatives: problem to solve, disagreement to resolve, matter to address, issue to confront, dispute to settle, grievance to air, concern to clarify, beef to hash out, objection to tackle, or complaint to address. These phrases all convey a similar sense of a conflict or difficulty that needs to be dealt with in some way. Choosing the right synonym partly depends on the context and tone of the conversation.