Struggling with two clues
4A. Junketing Washington diner at the end tips one? (10)
Have W?I?P?????
10A. Cutting edge in exploration company? Not the whole of it apparently? (5,3)
Have D?I??/???
Any help appreciated
If 'waitperson' is an American word for 'waiter', perhaps the 'wordplay' is that a person from Washington DC who went on a junket might end up tipping one (waiter)...?