Stalk or stem has a number (5)
I believe the answer is:
prowl
'stalk' is the definition.
(thesaurus)
'stem has a number' is the wordplay.
'stem' becomes 'prow' ('prow' can be a synonym of 'stem').
'has a number' becomes 'l' (I can't explain this - if you can you should believe this answer much more).
'prow'+'l'='PROWL'
'or' acts as a link.
Can you help me to learn more?
(Other definitions for prowl that I've seen before include "Creep around" , "Move in a predatory manner" , "Move about with unlawful intentions" , "Slink after prey" , "Move as if seeking prey" .)