Flip of a coin (4)
I believe the answer is:
toss
'flip of a coin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for toss that I've seen before include "Throw (coin or caber)" , "Raise a bit of money before opening" , "Throw with a light motion" , "Lob" , "Ship's movement" .)