Garden tool or key to the house (3)
I believe the answer is:
hoe
'garden tool' is the definition.
(tool used when gardening)
'key to the house' is the wordplay.
'key' becomes 'e' (musical key).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'the house' becomes 'ho' (abbreviation for house).
'e' put after 'ho' is 'HOE'.
'or' acts as a link.
(Other definitions for hoe that I've seen before include "Tool; promontory" , "Gardening tool" , "Garden tool with a flat blade" , "Plymouth - -" , "Weeder" .)