Eastern gallery welcomes study lacking teeth (8)
I believe the answer is:
edentate
'lacking teeth' is the definition.
(I've seen this before)
'eastern gallery welcomes study' is the wordplay.
'eastern' becomes 'e'.
'gallery' becomes 'tate' (I've seen this before).
'welcomes' means one lot of letters goes inside another (in sense of 'invites in').
'study' becomes 'den' (I've seen this before).
'e'+'tate'='etate'
'etate' going around 'den' is 'EDENTATE'.
(Other definitions for edentate that I've seen before include "sloth, for example" , "teeth? None" , "Mammal with few or no teeth" , "Gummy" , "Sloth, perhaps" .)