Public relations about the old town run smoothly (4)
I believe the answer is:
purr
'run smoothly' is the definition.
(I've seen this in another clue)
'public relations about the old town' is the wordplay.
'public relations' becomes 'PR' (abbreviation).
'about' means one lot of letters goes inside another.
'the old town' becomes 'ur' (I can't explain this - if you can you should give a lot more credence to this answer).
'pr' placed around 'ur' is 'PURR'.
Can you help me to learn more?
(Other definitions for purr that I've seen before include "Express pleasure" , "Sound of cat (or engine)" , "Happy feline sound" , "Cat's noise" , "Sound of a happy mog" .)