Claquer is a word with many meanings. The basic meaning is “to flap”, “to crack”, “to slam” (claquer la porte: “to slam the door”).
Colloquially, it also means “to spend money”.
T’as vraiment claqué cinquante balles dans un T-shirt ?!
Did you really spend fifty euros on a T-shirt?!
It can also mean “to die”, usually in an unexpected manner.
J’étais super malade la semaine dernière, j’ai cru que j’allais claquer.
I was really sick last week, I thought I was going to die.
Finally, the adjective claqué means “very tired”.
J’ai eu une longue journée, je suis claqué.
I had a long day, I’m exhausted.
Listen to the examples: