If you're trying to save genetics then do it. You should be able to keep it alive but it will take longer than if you took it in veg. You basically have to reveg the clone so it takes more time. If you're trying to just take clones regularly get em in veg.
i have a PPP 5 weeks in flower. Just took one branch tip off to try and clone it for this very reason to see how far into flower you can take clones and how fast they root and show growth.
Give me a week or two i'll tell how it works.