The board is a straight flush, but 6s has a higher straight flush. You can try to bluff the opponent off a chop in this situation, but you do run the risk of getting raised, which puts you in a tough spot. Because then you need to decide, if you want to call off your stack just hoping for a chop. I dont have any real opinion about this. This kind of spot comes up so rarely, that its not really, where edge is found or lost in the long run.
