It just shows what the high-ups get up to! (8)
I believe the answer is:
altitude
'it just shows what' is the definition.
The definition suggests a singular noun which matches the answer.
'high-ups get up to' is the wordplay.
I cannot quite see how this works, but
'high' could be 'alt' (I've seen this before) and 'alt' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'the' acts as a link.
Can you help me to learn more?
(Other definitions for altitude that I've seen before include "Lofty position" , "Height, elevation" , "high place" , "Angular distance above the horizon" , "Height above the earth's surface" .)