Provide online joke? (5)
I believe the answer is:
equip
'provide' is the definition.
(equipping is a kind of providing)
'online joke?' is the wordplay.
'online' becomes 'e' (as in e-mail or e-commerce).
'joke?' becomes 'quip' (quipping is a kind of joking).
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Supply (with items)" , "Pique (anag.)" , "Provide with suitable gear" , "Arm" , "Provide with items (for particular task)" .)