So far, one hasn't finished snowman (3)
I believe the answer is:
yet
'so far' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for yet that I've seen before include "Up till now" , "Up to this time and continuing" , "in spite of that" , "Still; however" , "Although" .)