Scope creep is when a client adds new requests; on top of their initial requests. At this point you have to optimize how much work you agree to do; versus how you can do it.
There are various circumstances to why scope creep might occur. The client might be new to the game, they aren't data driven, they have no solid awareness of what they can/can't do, and they ask for things they think are important (which aren't). The positives of scope creep are that your data is updated, you can show your commitment as a consultant, and it’s useful for a client to get rid of something they don't want and something they want. On the other hand the negatives of scope creep are that you're spreading yourself too thin and working on too much; which leads to unfulfilled tasks.
How would we deal with these circumstances? At this point, the PM would be the one making the decisions; the bigger the team, the bigger the project. Have communication with the team first and client after; then compare and contrast and make a decision. Then get everything in writing and make it into a prompt. If the client is in disagreement, provide easier alternatives and if they disagree inquire if they are able to maintain it.
Hope that helps you in your future client engagements!