There was only one runner here (4)
I believe the answer is:
iran
'there was only one runner here' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'one runner here' is the wordplay.
'one' becomes 'I' (Roman numeral).
'runner here' becomes 'ran' (I can't justify this - if you can you should believe this answer much more).
'i'+'ran'='IRAN'
Can you help me to learn more?
(Other definitions for iran that I've seen before include "It used to be Persia" , "Persia today" , "Farsi-speaking country" , "It was known as Persia until 1935" , "Previously known as Persia" .)