Bit of a necklace (4)
I believe the answer is:
bead
'bit of a necklace' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bead that I've seen before include "Drop of moisture; holed piece of glass" , "Small round piece of glass" , "Small ornamental strung ball" , "Necklace component" , "A bit of the rosary" .)