Burst out (5)
'burst out' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for erupt that I've seen before include "Blow up like volcano" , "Break out dramatically" , "Emit lava" , "go up" , "suddenly burst out" .)
(Other definitions for erupted that I've seen before include "Blew up or out as volcano may" , "Blew up like volcano" , "Broke out (like Etna)" , "Broke out suddenly" .)