Man soon consumes ton (5)
I believe the answer is:
anton
'man' is the definition.
(I've seen this before)
'soon consumes ton' is the wordplay.
'soon' becomes 'anon' (synonyms).
'consumes' means one lot of letters goes inside another.
'ton' becomes 't' ().
'anon' enclosing 't' is 'ANTON'.
(Other definitions for anton that I've seen before include "..... Chekov" , "Boy" , "- Chekhov, playwright" , "man" , "Chekhov, say" .)