First month to join hot website entertaining adult (9)
I believe the answer is:
inaugural
'first' is the definition.
(I know that first can be written as inaugural)
'month to join hot website entertaining adult' is the wordplay.
I cannot really understand how this works, but
'month' could be 'aug' (abbreviation for August) and 'aug' is found in the answer.
'hot' could be 'in' (both can mean fashionable) and 'in' is found within the answer.
'adult' could be 'a' (abbreviation) and 'a' is located in the answer.
The remaining letters 'url' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for inaugural that I've seen before include "Maiden" , "Relating to start of job or course" , "Introductory" , "It may be delivered" , "First address" .)