Twelve g? (8)
I believe the answer is:
midnight
'twelve' is the definition.
(twelve o'clock)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for midnight that I've seen before include "when it's usually dark" , "Dim thing seen at witching hour" , "12 hours from noon" , "possibly go to sleep this time?" , "When the day changes" .)