Move gradually for advantage (4)
I believe the answer is:
edge
This clue is a double definition.
'move gradually' is the first definition.
(to edge along slowly)
'for advantage' is the second definition.
(having the edge is having an advantage)
(Other definitions for edge that I've seen before include "on which one is ill at ease?" , "Border or cutting side of knife" , "Cutting side as of knife, or margin" , "Skirt" , "Rim or sharp side of knife" .)