Drainage spot (5)
I believe the answer is:
sewer
'drainage spot' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sewer that I've seen before include "Drain - seamstress?" , "Pipe to carry away waste matter" , "Waste-pipe" , "Large pipe for carrying waste matter" , "Channel to carry away waste water and matter" .)