In strata, having many sections, like an onion

Slang for a joke that isn't funny4 Forceful word often used before dunk in basketball4 European country with capital of Valletta5 Marie __, botanist and birth control campaigner6 An often-secret group who share an aim5 Audibly regret something6 Danish money, one hundredth of a krone3 Peruvian river, major tributary of Amazon7