He might publish media story without limits (6)
I believe the answer is:
editor
'he might publish' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'media story without limits' is the wordplay.
'media' becomes 'edi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'without limits' says to take the centre (letters at the edges or 'limits' are removed).
The centre of 'story' is 'tor'.
'edi'+'tor'='EDITOR'
Can you help me to learn more?
(Other definitions for editor that I've seen before include "Head of a newspaper say" , "Person responsible for publication;" , "Journalist - rioted (anag)" , "Do tire out the press person" , "Cudlipp, for one" .)