Supply at sea around a ton for animal (8)
I believe the answer is:
platypus
'for animal' is the definition.
(platypus is a kind of animal)
'supply at sea around a ton' is the wordplay.
'at sea' is an anagram indicator.
'around' indicates putting letters inside.
'ton' becomes 't' (abbreviation).
'supply' is an anagram of 'plypus'.
'a'+'t'='at'
'plypus' enclosing 'at' is 'PLATYPUS'.
(Other definitions for platypus that I've seen before include "One's billed in flat manner" , "Aussie creature" , "river creature" , "venomous mammal" , "Australian resident" .)