Angry rap music mainly revolving around money, essentially (2,2,4)
I believe the answer is:
up in arms
'angry' is the definition.
(I've seen this in another clue)
'rap music mainly revolving around money essentially' is the wordplay.
'mainly' means to remove the last letter.
'revolving' indicates an anagram (letters turning or twisting around).
'around' means one lot of letters goes inside another.
'essentially' means to look at the middle letters.
The central letter of 'money' is 'n'.
'rap'+'music'='rapmusic'
'rapmusic' with its final letter removed is 'rapmusi'.
'rapmusi' anagrammed gives 'upiarms'.
'upiarms' placed around 'n' is 'UP IN ARMS'.
(Other definitions for up in arms that I've seen before include "Protesting vigorously, ready for fight" , "Prepared to protest strongly" , "being angry" , "openly rebellious" , "Protesting strongly" .)