Where the pearl diver starts working (5)
I believe the answer is:
depth
'where' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'the pearl diver starts working' is the wordplay.
'starts' says to take the initial letters.
'working' indicates anagramming the letters.
The initial letters of 'pearl diver' is 'pd'.
'the'+'pd'='thepd'
'thepd' is an anagram of 'DEPTH'.
(Other definitions for depth that I've seen before include "Deepness" , "Measurement from front to back" , "sometimes leading to charge for sailors at war?" , "Distance from the surface to the bottom" , "Downward extent" .)