Actually more than a stone (3)
I believe the answer is:
ton
'actually more' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'a stone' is the wordplay.
'TON' is hidden within the letters.
However, I am uncertain how this is indicated.
'than' is the link.
Can you help me to learn more?
(Other definitions for ton that I've seen before include "Two thousand, two hundred and forty lbs avoirdupois" , "Style" , "Unit of weight equivalent to 20 cwts" , "Heavyweight" , "Twenty cwt" .)