Enemies in European and Irish rising (6)
I believe the answer is:
rivals
'enemies' is the definition.
(similar meaning)
'european and irish rising' is the wordplay.
'european' becomes 'slav' (I've seen this before).
'and' says to put letters next to each other.
'irish' becomes 'Ir' (abbreviation).
'rising' says the letters should be written in reverse (going up in a down clue).
'slav'+'ir'='slavir'
'slavir' reversed gives 'RIVALS'.
'in' acts as a link.
(Other definitions for rivals that I've seen before include "Opponents or competitors" , "Play by 1" , "Competitors or adversaries" , "Competitors, challengers" , "Persons in competition with each other" .)