Fluid-holding receptacle or tank (4)

I believe the answer is:

sump

(Other definitions for sump that I've seen before include "Crankcase reservoir" , "Reservoir for oil etc" , "oil well?" , "Cesspool" , "Engine oil reservoir" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.