A house key with too much on it, period! (7)
I believe the answer is:
cottage
'a house' is the definition.
(I know that cottage is a type of house)
'key with too much on it period' is the wordplay.
'key' becomes 'c' (musical key).
'with' is a charade indicator (letters next to each other).
'too much' becomes 'OTT' (short for over the top).
'on it' is a charade indicator (letters next to each other).
'period' becomes 'age' (age is a kind of period).
'c'+'ott'+'age'='COTTAGE'
(Other definitions for cottage that I've seen before include "bungalow" , "Small living space" , "Rural dwelling" , "Country residence" , "Small home" .)