Aviary, excessive inside small building (7)
I believe the answer is:
cottage
'small building' is the definition.
'aviary excessive inside' is the wordplay.
'aviary' becomes 'cage' (I've seen this before).
'excessive' becomes 'ott' (short for 'over the top').
'inside' indicates putting letters inside.
'cage' going around 'ott' is 'COTTAGE'.
(Other definitions for cottage that I've seen before include "Rural dwelling" , "Small single-storey dwelling" , "Cheese pie industries all may chase this" , "To make a home" , "Rural house" .)