Nail course of action (4)
I believe the answer is:
tack
I believe this clue is a double definition.
'nail' is the first definition.
(tack is a kind of nail)
'course of action' is the second definition.
(I've seen this before)
(Other definitions for tack that I've seen before include "Food; nail" , "vulgar" , "Drawing-pin" , "Stable gear" , "fix > riding gear" .)