Crossword Genius

Silly girl that is going out (5)

Ross

I believe the answer is:

inane

I'm a little stuck... Click here to teach me more about this clue!

'silly' is the definition.
(I've seen this in another clue)

'girl that is going out' is the wordplay.
I cannot quite see how this works, but
'girl' could be 'ina' and 'ina' is present in the answer.
The remaining letters 'ne' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for inane that I've seen before include "Without meaning or point" , "Mindlessly silly" , "Fatuous, vacuous" , "Moronic" , "Idiotic" .)

I've seen this clue in The Guardian, The Globe and Mail and The Telegraph.
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