Depressions in the hills? (5)
I believe the answer is:
downs
'the hills?' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for downs that I've seen before include "Drinks in one" , "Naturally part of SE England" , "Gently rolling hills" , "S. England chalk hills" , "Knocks over; drinks" .)