A mouse, for example, travelled north, ending in Belfast (6)
I believe the answer is:
rodent
'a mouse for example' is the definition.
(mouse is a kind of rodent)
'travelled north ending in belfast' is the wordplay.
'travelled' becomes 'rode' (eg travelled on a horse).
'north' becomes 'N' (abbreviation).
'ending in' says to take the final letters.
The last letter of 'belfast' is 't'.
'rode'+'n'+'t'='RODENT'
(Other definitions for rodent that I've seen before include "Eg, mouse or rat" , "Vermin" , "Mouse, squirrel or rat" , "Eg, mouse, squirrel" , "Mouse maybe" .)