Leaders of expedition travelling near a volcano (4)
I believe the answer is:
etna
'volcano' is the definition.
(Mount Etna)
'leaders of expedition travelling near a' is the wordplay.
'leaders of' says to take the initial letters.
The first letters of 'expedition travelling near' is 'etn'.
'etn'+'a'='ETNA'
(Other definitions for etna that I've seen before include "Neat volcano overturned" , "Mount . . . . is a volcano in Sicily" , "feature spewing lava" , "Sicilian hothead?" , "Impressive mount" .)