Conversion is done by inventor (6)
I believe the answer is:
edison
'inventor' is the definition.
(I know that Edison is a inventor)
'conversion is done by' is the wordplay.
'conversion' indicates an anagram.
'by' is a charade indicator (letters next to each other).
'is' after 'done' is 'doneis'.
'doneis' anagrammed gives 'EDISON'.
(Other definitions for edison that I've seen before include "The inventor is strangely onside" , "Thomas --, US?inventor" , "US scientist/inventor" , "Thomas Alva ......, great American inventor" , "Thomas Alva -, US inventor" .)