Person welcomed by good book group (5)
I believe the answer is:
nonet
'group' is the definition.
(group of nine musicians)
'person welcomed by good book' is the wordplay.
'person' becomes 'one' (I've seen this in other clues).
'welcomed by' indicates putting letters inside (letters welcomed inside).
'good book' becomes 'NT' (New Testament).
'one' going within 'nt' is 'NONET'.
(Other definitions for nonet that I've seen before include "Piece for nine musicians" , "Band of nine?" , "Composition for nine instruments" , "Composition for nine performers" , "group composition" .)