On way back, see about 250 in Greater Manchester town (6)
I believe the answer is:
eccles
'town' is the definition.
(I have seen 'northern town' mean 'eccles' so perhaps 'town' could also mean 'eccles')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for eccles that I've seen before include "Kind of cake or pastry filled with currants" , "Lancashire town" , "Greater Manchester town, producing its own special cakes since 1793" , "Goons char.; - cake" , "Town after which a cake is named" .)