Pleasant entertaining eastern relative (5)
I believe the answer is:
niece
'relative' is the definition.
(niece is a kind of relative)
'pleasant entertaining eastern' is the wordplay.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'entertaining' is an insertion indicator.
'eastern' becomes 'e'.
'nice' going around 'e' is 'NIECE'.
(Other definitions for niece that I've seen before include "One of the family" , "Preparation for curdling milk" , "Brother's girl" , "Kinswoman" , "Family relative" .)