In a depression look for somewhere to drink (6)
I believe the answer is:
trough
'in' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for trough that I've seen before include "basin" , "Container from which cattle or horses feed" , "Hollow; channel" , "Water manger" , "Container for watering or feeding animals" .)