Thin knife and some thin wooden wedges. It's one of those cases where it's better to increase the amount of 'damage' so that it can be better repaired. It may also be worthwhile watering down some Titebond to say 70:30 Titebond:water so that is penetrates the remaining crack areas at the ends that you can't get a small artist paint brush and full-strength Titebond in. It all helps. And if it really is a very small crack and you don't feel happy about opening it up, then you could mask off around it and wick in some thin CA and then clamp it down.