Joe, by the way, is the tenor (4)
I believe the answer is:
gist
'the tenor' is the definition.
(thesaurus)
'joe by the way' is the wordplay.
'joe' becomes 'gi' (GI Joe).
'by' says to put letters next to each other.
'the way' becomes 'st' (**).
'gi'+'st'='GIST'
'is' is the link.
(Other definitions for gist that I've seen before include "Core meaning" , "Substance of an argument" , "Essence; meaning" , "Main idea, kernel of matter" , "Central idea" .)