EU partner's terrible entrance (9)
I believe the answer is:
enrapture
'entrance' is the definition.
(thesaurus)
'eu partner's terrible' is the wordplay.
'terrible' indicates an anagram.
'eu'+'partner'='eupartner'
'eupartner' with letters rearranged gives 'ENRAPTURE'.
(Other definitions for enrapture that I've seen before include "Give intense pleasure to" , "Ape Turner (anag.)" , "Give delight to" , "Bewitch" , "entrance" .)