Nowadays has dossier rewritten about trivial ways (9)

'rewritten about trivial ways' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'nowadays has dossier' is the wordplay.
I cannot quite understand how this works, but
'nowadays' could be 'ad' (AD, Anno Domini, as opposed to BC, Before Christ) and 'ad' is present in the answer.
an anagram of 'dossier' is 'sideros' which is within the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?