Pleasant to welcome English relative (5)
I believe the answer is:
Here is my best explanation:
'relative' is the definition.
(niece is a kind of relative)
'pleasant to welcome english' is the subsidiary indication.
'pleasant' becomes 'nice' ('nice' can be similar in meaning to 'pleasant').
'to welcome' is an insertion indicator (in sense of 'inviting in').
'english' becomes 'e' (abbreviation).
'nice' enclosing 'e' is 'niece'.
(Other definitions for niece that I've seen before include "A sibling's daughter", "Girl", "Relative", "[PRIEST'S] daughter?", "Kinswoman", "A younger female relative", "One of the family", "Family relation", "A young female relative" and "Brother's girl".)