Mr Runyan comes up; he has no settled occupation (5)
I believe the answer is:
nomad
'mr runyan comes up he has no settled occupation' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he has no settled occupation' is the wordplay.
'he' becomes 'Ad'.
'has' is a charade indicator (letters next to each other).
'no settled occupation' becomes 'nom' (I am not sure about this - if you are sure you should believe this answer much more).
'ad' after 'nom' is 'NOMAD'.
Can you help me to learn more?
(Other definitions for nomad that I've seen before include "Migrant" , "Member of travelling people" , "Traveller with no permanent home" , "Person wandering" , "is one unsettled?" .)