Being most upset about the ringleader, rage wildly (5)
I believe the answer is:
storm
'rage wildly' is the definition.
'storm' can be an answer for 'rage' (synonyms). I'm not sure about the 'wildly' bit.
'being most upset about the ringleader' is the wordplay.
'being most' becomes 'mots' (I can't justify this - if you can you should believe this answer much more).
'upset' says the letters should be written backwards.
'about' is an insertion indicator.
'the ringleader' becomes 'r' (first letter of ring).
'mots' in reverse letter order is 'stom'.
'stom' enclosing 'r' is 'STORM'.
Can you help me to learn more?
(Other definitions for storm that I've seen before include "Sandy, perhaps" , "rave" , "Awful blow" , "Wind force 10 on Beaufort scale" , "Violent outburst" .)