Final recourse (4-5)
I believe the answer is:
last-ditch
'final recourse' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for last-ditch that I've seen before include "Final recourse" , "Eleventh hour" , "Stitch lad up in final defence" , "Denoting final attempt (to do something)" , "Of an attempt or stand, final and desperate" .)