Brussels protecting Poles with, ultimately, positive result (5)
I believe the answer is:
ensue
'result' is the definition.
('ensue' can be a synonym of 'result')
'brussels protecting poles with ultimately positive' is the wordplay.
'brussels' becomes 'eu' (Brussels is a metonym for the European Union).
'protecting' means one lot of letters goes inside another.
'poles' becomes 'ns' (North and South poles).
'with' says to put letters next to each other.
'ultimately' says to take the final letters.
The final letter of 'positive' is 'e'.
'eu' going around 'ns' is 'ensu'.
'ensu'+'e'='ENSUE'
(Other definitions for ensue that I've seen before include "Proceed" , "Happen or come about as consequence" , "Happen afterwards as a result" , "Befall" , "Turn out" .)