Depression in the field? (5)
I believe the answer is:
gully
'depression' is the definition.
(gully is a kind of depression)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for gully that I've seen before include "one in the field" , "Water-worn ravine - fielding position" , "Rainwater channel" , "Fielding position -- narrow channel" , "Ravine cut by running water" .)