Token bit of venom in a large container (7)
I believe the answer is:
nominal
'token' is the definition.
(I know that token can be written as nominal)
'bit of venom in a large container' is the wordplay.
'bit of' indicates a hidden word.
'NOMINAL' is hidden within 'venom in a large container'.
(Other definitions for nominal that I've seen before include "Peppercorn rent" , "Ostensible" , "In name only or of token value (7)" , "Inconsiderable" , "Token - lion-man (anag)" .)