Pipe stout beer evenly (4)
I believe the answer is:
tube
'pipe' is the definition.
(I know that pipe can be written as tube)
'stout beer evenly' is the wordplay.
'evenly' indicates alternate letters (the letters in even-numbered positions).
'stout'+'beer'='stoutbeer'
The alternating letters of 'stoutbeer' are 'TUBE'.
(Other definitions for tube that I've seen before include "London Underground or long cylinder" , "channel" , "Pipe - railway" , "Can of beer (colloquial)" , "Hollow cylindrical object" .)