PM, happy individual after socialist's left discontented (9)
I believe the answer is:
gladstone
'pm' is the definition.
(Victorian UK prime minister William Gladstone)
'happy individual after socialist's left discontented' is the wordplay.
I cannot quite understand how this works, but
'happy' could be 'glad' (similar in meaning) and 'glad' is present in the answer.
'individual' could be 'one' (an individual is one person) and 'one' is present in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for gladstone that I've seen before include "Liberal leader" , "C. nineteenth Liberal prime minister" , "Bag for a former British statesman" , "So tangled up with old British Prime Minister" , "5,27 [PRIME MINISTER]" .)