Happy to do what Jason wanted? (6,6)
I believe the answer is:
golden fleece
'jason wanted?' is the definition.
I can't judge whether this definition defines the answer.
'happy to do' is the wordplay.
'happy' becomes 'golden' (similar in meaning).
'to do' becomes 'fleece' (both can mean to scam).
'golden'+'fleece'='GOLDEN FLEECE'
'what' acts as a link.
Can you help me to learn more?
(Other definitions for golden fleece that I've seen before include "Item taken by Jason and the Argonauts" , "Argonauts sought it (Gk. myth)" , "What Jason sought" , "Object of Jason's quest" .)