Beatrice given diamonds, perhaps part of necklace (4)
I believe the answer is:
bead
'part of necklace' is the definition.
(a necklace might be made up of beads)
'beatrice given diamonds' is the wordplay.
'beatrice' becomes 'Bea' (Bea is short for Beatrice).
'given' says to put letters next to each other.
'diamonds' becomes 'd' (abbreviation in bridge say).
'bea'+'d'='BEAD'
'perhaps' acts as a link.
(Other definitions for bead that I've seen before include "Small ornamental strung ball" , "A bit of the rosary" , "Glass ball" , "bit off necklace, say" , "Necklace element" .)