Supply election's first gag (5)
I believe the answer is:
equip
'supply' is the definition.
(equipping is a kind of supplying)
'election's first gag' is the wordplay.
'first' suggests taking the first letters.
'gag' becomes 'quip' ('quip' can be a synonym of 'gag').
The first letter of 'elections' is 'e'.
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Pique (anag.)" , "Accoutre" , "Provide with stock" , "Supply with what is needed" , "Outfit" .)