Come before volcano in retreat and surrender (8)
I believe the answer is:
antecede
'come before' is the definition.
(thesaurus)
'volcano in retreat and surrender' is the wordplay.
'volcano' becomes 'etna' (Etna is an example).
'in retreat' says the letters should be written in reverse.
'and' says to put letters next to each other.
'surrender' becomes 'cede' ('cede' can be a synonym of 'surrender').
'etna' back-to-front is 'ante'.
'ante'+'cede'='ANTECEDE'
(Other definitions for antecede that I've seen before include "go before, in rank" , "Lead" .)