Of indeterminate age and not popular with the boys? (8)
I believe the answer is:
dateless
'of indeterminate age and' is the definition.
I can't judge whether this definition defines the answer.
'not popular with the boys?' is the wordplay.
I cannot really see how this works, but
'not' could be 'less' (I've seen this in other clues) and 'less' is present in the answer.
The remaining letters 'date' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for dateless that I've seen is " lacking a boyfriend to go out with?".)