Problem in public transport when going round part of town (6)
I believe the answer is:
suburb
'part of town' is the definition.
'problem in public transport when going round' is the wordplay.
'problem' becomes 'rub'.
'in' means one lot of letters goes inside another.
'public transport' becomes 'bus' (bus is a kind of public transport).
'when going round' says the letters should be written backwards.
'rub' going into 'bus' is 'brubus'.
'brubus' written backwards gives 'SUBURB'.
(Other definitions for suburb that I've seen before include "District adjoining a town" , "Area on the outskirts of a city" , "Residential district on a city's outskirts" , "Outer town area" , "Residential district on the outskirts of a city" .)