Actor to go for lovelorn emperor (7)
I believe the answer is:
costner
'lovelorn emperor' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'actor to go for' is the wordplay.
'actor' becomes 'ner' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' says to put letters next to each other (I've seen this in other clues).
'go for' becomes 'cost' (I've seen this in another clue).
'ner' put after 'cost' is 'COSTNER'.
Can you help me to learn more?
(Another definition for costner that I've seen is " US actor".)