Anteater, say, in gallery at the back of garden (8)
I believe the answer is:
edentate
'anteater say' is the definition.
(I know that New World anteater is a type of edentate)
'gallery at the back of garden' is the wordplay.
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'at the back of' says to put letters next to each other.
'garden' becomes 'eden' (Garden of Eden in the Bible).
'tate' put after 'eden' is 'EDENTATE'.
'in' is the link.
(Other definitions for edentate that I've seen before include "Toothless creature" , "Toothless mammal" , "Mammal with few or no teeth" , "Animal as sloth, armadillo" , "Mammal such as sloth or anteater" .)