Greek character, famous, returned and set off (8)
I believe the answer is:
detonate
'set off' is the definition.
('detonate' can be a synonym of 'set off')
'greek character famous returned' is the wordplay.
'greek character' becomes 'eta' (letter from the Greek alphabet).
'famous' becomes 'noted' ('noted' can be a synonym of 'famous').
'returned' says the letters should be written backwards.
'eta'+'noted'='etanoted'
'etanoted' backwards is 'DETONATE'.
'and' is the link.
(Other definitions for detonate that I've seen before include "Cause to explode" , "Discharge" , "Start 15 [EXPLOSION]" , "go off with a bang" , "Blow up, explode" .)