Could become neat volcano (4)
I believe the answer is:
etna
'volcano' is the definition.
(Mount Etna)
'could become neat' is the wordplay.
'could become' indicates anagramming the letters.
'neat' anagrammed gives 'ETNA'.
(Other definitions for etna that I've seen before include "a mount hotly tipped when it runs" , "Heating vessel" , "Constant smoker" , "Europe's highest active volcano" , "Threatening mountain" .)