Plant stem (5)
(Other definitions for tuber that I've seen before include "Underground stem, root" , "Fleshy underground part of a stem, often used as food" , "Rhizome, as of potato" , "Potato, for example" , "or still vegetating?" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plant stem</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for stalk that I've seen before include "Follow prey stealthily" , "Shadow" , "Follow sneakily" , "Stem; pursue stealthily" , "Quietly pursue" .)