Bit of condensation (4)
I believe the answer is:
bead
'bit of condensation' 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 "Round piece of glass, etc" , "Small round piece of glass" , "Drop of liquid on a surface" , "Necklace piece; droplet" , "Small ball with a hole through the middle" .)