Nearly spill over edges (4)
I believe the answer is:
lips
'edges' is the definition.
(lip is a kind of edge)
'nearly spill over' is the wordplay.
'nearly' means to remove the last letter.
'over' shows that the letters should be reversed in order.
'spill' with its final letter taken off is 'spil'.
'spil' in reverse letter order is 'LIPS'.
(Other definitions for lips that I've seen before include "Edges of the mouth" , "Fleshy folds on the face" , "margins" , "Fleshy folds of tissue" , "Olivia's two, 'indifferent red' (T. Night)" .)