Pleasant to have European relation (5)
I believe the answer is:
niece
'relation' is the definition.
(niece is a kind of relation)
'pleasant to have european' is the wordplay.
'pleasant' becomes 'nice' (associated in meaning).
'to have' is an insertion indicator.
'european' becomes 'E' (abbreviation e.g. EU).
'nice' enclosing 'e' is 'NIECE'.
(Other definitions for niece that I've seen before include "Brother's daughter" , "Female family member" , "A younger female relative" , "Family relative" , "Preparation for curdling milk" .)