As a journalist he has to ride all over the place (6)
I believe the answer is:
editor
'as a journalist he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'to ride all over the place' is the wordplay.
'all over the place' indicates anagramming the letters.
'to'+'ride'='toride'
'toride' is an anagram of 'EDITOR'.
'has' acts as a link.
Can you help me to learn more?
(Other definitions for editor that I've seen before include "Person in charge of paper" , "Director of 3 down" , "Do tire out the newspaper head" , "Media boss" , "One responsible for leader" .)