Antonio's heavy heart (3)
I believe the answer is:
ton
'heavy heart' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'antonio's' is the wordplay.
'TON' is hidden within the letters.
However, I'm unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for ton that I've seen before include "1000 kilos" , "Two thousand - two hundred and forty pounds" , "Twenty cwt" , "Fashionable" , "People of fashion" .)