Musk, say, adopting revolutionary arrangement of forces (7)
I believe the answer is:
echelon
'arrangement of forces' is the definition.
The answer and definition can be both groups as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'musk say adopting revolutionary' is the wordplay.
'musk say' becomes 'elon' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'adopting' is an insertion indicator (inserted letters are taken on or adopted).
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'elon' placed around 'che' is 'ECHELON'.
Can you help me to learn more?
(Other definitions for echelon that I've seen before include "Leech on (anag.)" , "Ladder formation" , "Staggering display of military" , "Wedge-shaped formation of troops" , "Degree" .)