Down and back, butterfly (11)
I believe the answer is:
swallowtail
'butterfly' is the definition.
(I've seen this before)
'down and back' is the wordplay.
'down' becomes 'swallow' (both can mean to consume or eat).
'and' says to put letters next to each other.
'back' becomes 'tail' (tail is a kind of back).
'swallow'+'tail'='SWALLOWTAIL'
(Other definitions for swallowtail that I've seen before include "coat" , "In circle, mythical snake does" , "Butterfly" , "insect" .)