Toledo ports agree to box up creature (9)
I believe the answer is:
gastropod
'creature' is the definition.
(gastropod is a kind of creature)
'toledo ports agree to box up' is the wordplay.
'to box' indicates the answer is hidden within the clue (I've seen 'boxes' mean this (to box can mean to contain)).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'doportsag' is hidden within 'toledo ports agree'.
'doportsag' written backwards gives 'GASTROPOD'.
(Other definitions for gastropod that I've seen before include "Shellfish" , "slug, perhaps" , "Eg, a snail or slug" , "Escargot" , "Mollusc such as snail or limpet" .)