Not quite finished a bit more help appreciated 15a Noble, when having no answer, is put in danger (7) 18a TV presenter has backed interior artist with loud colour (5,6) 21a Restaurant grub is tropical to some extent (6)
15a - imperil. imperial minus the a for answer.
18a - Sarah Greene. has with RA in backwards + greene, sounds like green.
21a - bistro. contained in the words gruB IS TROpical.