broody hen

[mastiffs07]

Can I put 5-6 day old chick under a broody hen?

 

[Ol Grey Mare]

You can try - but at that point you are outside of the optimal window of time for attempting an adoption. If you decide to try it just be extra vigilant (but from a distance so as not to add stress to the situation which would increase the chance of rejection) and prepared to react if necessary in having an alternate brooder situation available. Also, I notice you say "a" chick - you'll want to have more than one chick, three or more being better.