Pipe; underground railway (4)
I believe the answer is:
tube
(Other definitions for tube that I've seen before include "Pipe - railway" , "Can of beer (colloquial)" , "channel" , "Transport system" , "Hollow body for the underground" .)
I believe the answer is:
tube
(Other definitions for tube that I've seen before include "Pipe - railway" , "Can of beer (colloquial)" , "channel" , "Transport system" , "Hollow body for the underground" .)