Prepare online joke? (5)
I believe the answer is:
equip
'prepare' is the definition.
(thesaurus)
'online joke?' is the wordplay.
'online' becomes 'e' (abbreviation for electronic, e.g. in ecommerce).
'joke?' becomes 'quip' (quipping is a kind of joking).
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Pique (anag.)" , "Provide stuff" , "Outfit" , "Provide with stock" , "Provide with items (for particular task)" .)