Given to sudden outbursts (8)
I believe the answer is:
volcanic
'given to sudden outbursts' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for volcanic that I've seen before include "given to sudden outbursts" , "Describing lava?" , "Of lava-producing fissures" , "Liable to violent outbursts" , "Relating to eruption in earth's surface" .)