Crossword Genius

Uncool name Niobe used now and then (4,2,1,4,4)

Ross

I believe the answer is:

once in a blue moon

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

'and then' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'uncool name niobe used' is the wordplay.
'used' indicates an anagram.
'uncool'+'name'+'niobe'='uncoolnameniobe'
'uncoolnameniobe' is an anagram of 'ONCE IN A BLUE MOON'.

'now' is the link.

Can you help me to learn more?

(Other definitions for once in a blue moon that I've seen before include "very rarely" , "very occasionally" , "Hardly ever (4,2,1,4,4)" , "with extremely low frequency'" , "on very rare occasions" .)

I've seen this clue in The Daily Express.
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