My heart wants love ultimately (3)
I believe the answer is:
cor
'my' is the definition.
(both are expressions of surprise)
'heart wants love ultimately' is the wordplay.
'heart' means to look at the middle letters.
'wants' becomes 'lacks' ('lack' can be a synonym of 'want').
'love ultimately' becomes 'or' (I can't justify this - if you can you should give a lot more credence to this answer).
The middle letter of 'lacks' is 'c'.
'c'+'or'='COR'
Can you help me to learn more?
(Other definitions for cor that I've seen before include "Gosh" , "Blimey" , "Expression of surprise" , "Surprised expression" .)