In London, a director’s lowest point (5)
I believe the answer is:
nadir
'lowest point' is the definition.
'in london a director's' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NADIR' is hidden in the letters of 'london a directors'.
(Other definitions for nadir that I've seen before include "It's the depths" , "Low spot" , "Low-water mark" , "Low point" , "Lower one cannot get!" .)