Drain problem (4)
I believe the answer is:
clog
'drain problem' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for clog that I've seen before include "Block up - type of shoe" , "Become blocked with wooden-soled shoe" , "Dutch shoe" , "Block with wooden-soled shoe?" , "Wooden footwear" .)