Runner or dramatist in play (13)
I believe the answer is:
administrator
'runner' is the definition.
(in the sense of someone who runs things)
'or dramatist in play' is the wordplay.
'play' indicates anagramming the letters.
'or'+'dramatist'+'in'='ordramatistin'
'ordramatistin' anagrammed gives 'ADMINISTRATOR'.
(Other definitions for administrator that I've seen before include "Manager, controller" , "Business organiser" , "one controls" , "Executive" , "Official organiser" .)