Pleasant hosting European relative (5)
I believe the answer is:
niece
'relative' is the definition.
(niece is a kind of relative)
'pleasant hosting european' is the wordplay.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'hosting' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'nice' enclosing 'e' is 'NIECE'.
(Other definitions for niece that I've seen before include "member of different generation" , "Female family member" , "Family relative" , "A younger female relative" , "Family girl" .)