Course of action queen, perhaps, set up with king (4)
I believe the answer is:
tack
'course of action' is the definition.
(I've seen this before)
'queen perhaps set up with king' is the wordplay.
'queen perhaps' becomes 'cat' (a female cat is a queen).
'set up' says the letters should be written backwards.
'with' says to put letters next to each other.
'king' becomes 'k'.
'cat' backwards is 'tac'.
'tac'+'k'='TACK'
(Other definitions for tack that I've seen before include "Drawing-pin" , "Alter course - riding gear" , "Small broad-headed nail" , "Nail; course of action" , "Small nail; sail (boat) against the wind" .)