Pleasant to have English relative (5)
I believe the answer is:
niece
'relative' is the definition.
(niece is a kind of relative)
'pleasant to have english' is the wordplay.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'to have' indicates putting letters inside.
'english' becomes 'e' (abbreviation).
'nice' enclosing 'e' is 'NIECE'.
(Other definitions for niece that I've seen before include "Brother's daughter" , "Family girl" , "Preparation for curdling milk" , "member of different generation" , "Brother or sister's daughter" .)