Made tip go under top of spark plug (6)
I believe the answer is:
spigot
'plug' is the definition.
(I know that spigot is a type of plug)
'made tip go under top of spark' is the wordplay.
'made' is an anagram indicator.
'under' is a charade indicator (letters next to each other) (below, in a down clue).
'top of' says to take the initial letters.
The first letter of 'spark' is 's'.
'tip'+'go'='tipgo'
'tipgo' with letters rearranged gives 'pigot'.
'pigot' put after 's' is 'SPIGOT'.
(Other definitions for spigot that I've seen before include "Peg - plug - tap" , "Plug - an American tap" , "Tap, faucet" , "Peg to seal vent in cask" , "Tap for barrel" .)