Stem or stalk pruned (4)
I believe the answer is:
tube
'stem' is the definition.
(thesaurus)
'stalk pruned' is the wordplay.
'stalk' becomes 'tuber' (tuber is a kind of stalk).
'pruned' means to remove the last letter.
'tuber' with its last letter taken off is 'TUBE'.
'or' acts as a link.
(Other definitions for tube that I've seen before include "Pipe (with trains?)" , "Long, hollow cylinder" , "Pipe or hose" , "Cylindrical hollow conduit" , "London Underground or long cylinder" .)