Ruler ever so unusual, one given good name (9)
I believe the answer is:
sovereign
'ruler' is the definition.
(sovereign is a kind of ruler)
'ever so unusual one given good name' is the wordplay.
'unusual' indicates anagramming the letters.
'one' becomes 'i' (Roman numeral).
'given' means one lot of letters go next to another.
'good' becomes 'g' (abbreviation).
'name' becomes 'n' (common abbreviation e.g. on forms).
'ever'+'so'='everso'
'everso' with letters rearranged gives 'sovere'.
'sovere'+'i'+'g'+'n'='SOVEREIGN'
(Other definitions for sovereign that I've seen before include "13 across -- coin" , "Supreme ruler" , "Head of state" , "Old gold coin" , "more than a prince" .)