Possibly not a weight? (3)

I believe the answer is:

ton

'a weight?' is the definition.
(unit of weight)

'possibly not' is the wordplay.
'possibly' indicates an anagram.
'not' is an anagram of 'TON'.

(Other definitions for ton that I've seen before include "100 mph, runs, etc" , "Unit of weight equivalent to 2240 pounds" , "Heavyweight" , "Imperial unit of weight" , "Fashionable" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app