Turn up before it erupts (4)
I believe the answer is:
etna
'it erupts' is the definition.
The definition suggests a singular noun which matches the answer.
'turn up before' is the wordplay.
'turn up' says the letters should be written backwards.
'before' becomes 'ante' (prefix meaning before).
'ante' back-to-front is 'ETNA'.
Can you help me to learn more?
(Other definitions for etna that I've seen before include "Neat class of volcano in Sicily" , "It sometimes blows its top" , "Heating vessel" , "smoker in Sicily" , "burning mountain" .)