Expression of disgust by a Persian noble (4)
I believe the answer is:
agha
'expression of disgust' is the definition.
The definition suggests a singular noun which matches the answer.
'by a persian noble' is the wordplay.
'by' says to put letters next to each other.
'persian noble' becomes 'agh' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a' put after 'agh' is 'AGHA'.
Can you help me to learn more?
(Other definitions for agha that I've seen before include "Turkish civil or military leader" , "Ruler" , "Turkish officer" , "Alternative spelling for a Turkish commander" .)