Drop of sweat (4)
I believe the answer is:
bead
'drop of sweat' 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 liquid on a surface" , "Round piece of glass, etc" , "Drop, part of rosary" , "Necklace component" , "Small round piece of glass" .)