Vain, so no dates? (9)
I believe the answer is:
fruitless
'vain' is the definition.
(I know that vain can be written as fruitless)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for fruitless that I've seen before include "Vain" , "failing to achieve the desired results" , "Unproductive" , "being without dates, perhaps" , "Unprofitable" .)