Stock online joke? (5)
I believe the answer is:
equip
'stock' is the definition.
(thesaurus)
'online joke?' is the wordplay.
'online' becomes 'e' (as in e-mail or e-commerce).
'joke?' becomes 'quip' (a quip is a joke or witticism).
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Supply (with kit)" , "Give what's needed" , "Furnish with supplies" , "Provide everything that is required'" , "Fit out, supply" .)