Before the volcano goes up! (4)
I believe the answer is:
ante
'before' is the definition.
(I've seen this before)
'volcano goes up' is the wordplay.
'volcano' becomes 'etna' (Mount Etna).
'goes up' says the letters should be written in reverse.
'etna' reversed gives 'ANTE'.
'the' is the link.
(Other definitions for ante that I've seen before include "Stake, bet" , "Gaming stake" , "expected from stake" , "Initial bet" , "Fixed stake" .)