Worrisome trend doubling as essential members drop out (9)
I believe the answer is:
troubling
'worrisome' is the definition.
(I know that worrisome can be written as troubling)
'trend doubling as essential members drop out' is the wordplay.
I cannot really understand how this works, but
'as' could be 'in' (I've seen this in other clues) and 'in' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for troubling that I've seen before include "causing distress" , "Burdensome" .)