On the way to Oslo, changed seats (6)
I believe the answer is:
stools
'seats' is the definition.
(stool is a kind of seat)
'on the way to oslo changed' is the wordplay.
'on' indicates putting letters inside (as in clothing \'on\' a person).
'the way' becomes 'st' ().
'changed' indicates an anagram.
'oslo' anagrammed gives 'ools'.
'st' put within 'ools' is 'STOOLS'.
(Other definitions for stools that I've seen before include "Seats without backs or arms" , "Simple seats, without back or arms" .)