Now and again (8)
This clue might be a double definition.
'now' is the first definition.
Both the answer and definition are adverbs. Maybe you can see an association between them that I can't see?
'again' is the second definition.
(I've seen this in another clue)
'and' acts as a link.
Can you help me to learn more?
(Other definitions for twice that I've seen before include "Double in quantity" , "Doubly" , "Two times" , "You only live -- (film)" .)
'now and again' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for every so often that I've seen before include "At intervals" , "Occasionally" .)