Totally with it, depending on the trifling (2-2-3-6)
I believe the answer is:
up-to-the-minute
'totally with it' is the definition.
I can't judge whether this defines the answer.
'depending on the trifling' is the wordplay.
'depending' becomes 'upto' (I am not sure about this - if you are sure you should believe this answer much more).
'on' says to put letters next to each other.
'trifling' becomes 'minute' (I've seen this in another clue).
'upto'+'the'+'minute'='UP-TO-THE-MINUTE'
Can you help me to learn more?
(Other definitions for up-to-the-minute that I've seen before include "Incorporating the very latest developments" , "Current" , "Right now" , "Tie up the mount? (anag)" , "Extremely modern" .)