Much elevated in the air force (3)
I believe the answer is:
far
'much' is the definition.
(I've seen this in another clue)
'elevated in the air force' is the wordplay.
'elevated' says the letters should be written backwards (in a down clue, letters go up).
'in the air' becomes 'ra' (I can't explain this - if you can you should give a lot more credence to this answer).
'force' becomes 'f' (scientific abbreviation).
'ra'+'f'='raf'
'raf' in reverse letter order is 'FAR'.
Can you help me to learn more?
(Other definitions for far that I've seen before include "Distant" , "Very much" , "Remote" , "At a great distance way" , "A long, long way to go" .)