I’m disgusted about leader of socialist party (4)
I believe the answer is:
bash
'party' is the definition.
(term for a party or celebration)
'i'm disgusted about leader of socialist' is the wordplay.
'i'm disgusted' becomes 'bah' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' means one lot of letters goes inside another.
'leader of' indicates taking the first letters.
The initial letter of 'socialist' is 's'.
'bah' going around 's' is 'BASH'.
Can you help me to learn more?
(Other definitions for bash that I've seen before include "Party (colloq.)" , "Smite; a party" , "social occasion" , "Heavy blow; party" , "Dent - party" .)