Good one, sovereign trailblazer (7)
I believe the answer is:
pioneer
'trailblazer' is the definition.
(both can mean an innovator)
'good one sovereign' is the wordplay.
'good' becomes 'pi' (old-fashioned term for pious).
'sovereign' becomes 'er' (Abbreviation for Elizabeth Regina).
'pi'+'one'+'er'='PIONEER'
(Other definitions for pioneer that I've seen before include "Colonist" , "Research leader" , "Founder" , "take the lead" , "spacecraft" .)