stuck with a few this week (just moved house and brain numb at moment!) - any help
12a a branch from the vascular system of a plant's stem (4-5) l-a- t---- (leaf?)
16a pigeon that turns back-somersaults in the air (7) ----l r
17d an undecied or disputed issue (4,5) --o- ----t
20d citizenb of capital of egypt (7) c---e-e
23a a little pit made by a raindrop in clay etc some times preserved in rocks (4-5) r--- ----t