Part of action, a director’s lowest point (5)
I believe the answer is:
nadir
'lowest point' is the definition.
(I've seen this before)
'part of action a director's' is the wordplay.
'part of' indicates a hidden word.
'NADIR' is hidden in the letters of 'action a directors'.
(Other definitions for nadir that I've seen before include "All-time low" , "The lowest point of anything" , "worst-case scenario?" , "Dinar (anag.)" , "deep despair" .)