Change the order in a McDonald’s (4)
I believe the answer is:
perm
'change the order' is the definition.
(perm can mean to create a new permutation)
'a mcdonald's' is the wordplay.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'mcdonald's' becomes 'M' (fast food franchise known for its yellow M logo).
'per'+'m'='PERM'
'in' acts as a link.
(Other definitions for perm that I've seen before include "Hairdo - combination on football pools" , "To curl (hair)" , "Give a wave" , "combo in pools" , "Russian city and hairstyle, in short" .)