More than a ton weight! (5)
I believe the answer is:
stone
'weight' is the definition.
(stone is a unit of weight)
'more than a ton' is the wordplay.
I cannot quite see how this works, but
'a' could be 'one' and 'one' is found within the answer.
'ton' could be 't' (abbreviation) and 't' is present in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stone that I've seen before include "Gem; Staffs. town" , "Kernel" , "Seed of e.g. cherry" , "Rock; fruit seed" , "Rock; cherry seed" .)