Once more, it's not an old word (4)
I believe the answer is:
anew
'once more' is the definition.
(I've seen this in another clue)
'not an old word' is the wordplay.
I cannot really see how this works, but
'an' could be 'a' and 'a' is present in the answer.
The remaining letters 'new' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'it's' is the link.
Can you help me to learn more?
(Other definitions for anew that I've seen before include "Again but differently" , "Afresh" , "Once more (poetic)" , "Wane in a different way, again" , "From the beginning again" .)