Europeans sealing United’s second defeat on the road (2,5)
I believe the answer is:
en route
'on the road' is the definition.
(I've seen this before)
'europeans sealing united's second defeat' is the wordplay.
'europeans' becomes 'ee' (an abbreviation for European written twice).
'sealing' indicates putting letters inside (inserted letters are sealed inside).
'united's second' becomes 'n' (ond letter of 'united').
'defeat' becomes 'rout' (rout is a kind of defeat).
'n'+'rout'='nrout'
'ee' going around 'nrout' is 'EN ROUTE'.
(Other definitions for en route that I've seen before include "In transit (French)" , "on the road" , "March" , "While travelling" , "On the way - in France" .)