Provide them with the necessary material for first entertaining joke (5)
I believe the answer is:
equip
'provide' is the definition.
(I know that equip is a more specific form of the action provide)
'first entertaining joke' is the wordplay.
'first entertaining' becomes 'e' (1st letter of 'entertaining').
'joke' becomes 'quip' (quipping is a kind of joking).
'e'+'quip'='EQUIP'
'them with the necessary material for' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for equip that I've seen before include "Give what's needed" , "Give kit to" , "Supply with what is needed" , "Furnish with requirements" , "Sally" .)