Former situation on a golf green in which an opponent's ball blocked the line between the hole and the ball about to be played (6)
I believe the answer is:
stymie
(Other definitions for stymie that I've seen before include "Thwart - block - my site (anag)" , "Situation from which it is almost impossible to proceed" , "Block; hinder" , "Prevent (by getting in the way)" , "Block or thwart an activity" .)