My staff reduced almost everything - that’s obscure (8)
I believe the answer is:
mystical
'that's obscure' is the definition.
(thesaurus)
'my staff reduced almost' is the wordplay.
'reduced' says to take the initial letters (the word is reduced to its first letter).
'almost' becomes 'tical' (I can't justify this - if you can you should believe this answer much more).
The first letter of 'staff' is 's'.
'my'+'s'+'tical'='MYSTICAL'
'everything' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for mystical that I've seen before include "Sacredly obscure" , "Inspiring spiritual awe" , "of occult rites" , "'Esoteric, spiritual (8)'" , "Slimy act? (anag)" .)