A can brought back on first day with a snake (8)
I believe the answer is:
anaconda
'snake' is the definition.
(anaconda is a kind of snake)
'a can brought back on first day with a' is the wordplay.
'brought back' says the letters should be written backwards.
'first day' becomes 'd' (1st letter of 'day').
'with' means one lot of letters go next to another.
'can' in reverse letter order is 'nac'.
'a'+'nac'+'on'+'d'+'a'='ANACONDA'
(Other definitions for anaconda that I've seen before include "Strangler" , "A slippery customer" , "Large South America snake" , "South American killer" , "Aquatic snake" .)