Greek character describing northern volcano (4)
I believe the answer is:
etna
'volcano' is the definition.
(Etna is an example)
'greek character describing northern' is the wordplay.
'greek character' becomes 'eta' (letter from the Greek alphabet).
'describing' is an insertion indicator (describe can mean to form the outline of).
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'eta' going around 'n' is 'ETNA'.
(Other definitions for etna that I've seen before include "Impressive mount" , "one blowing top?" , "high peak" , "It could erupt" , "Volcano; reverse of stake" .)