Supply European with joke (5)
I believe the answer is:
equip
'supply' is the definition.
(equipping is a kind of supplying)
'european with joke' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'with' is a charade indicator (letters next to each other).
'joke' becomes 'quip' (a quip is a joke or witticism).
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Fit out, supply" , "Arm" , "Give what's needed" , "Provide with stock" , "Pique (anag.)" .)