Cowardliness - trait originally cultivated in royal household (7,6)
I believe the answer is:
Here is my best explanation:
'royal household' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'cowardliness trait originally cultivated' is the subsidiary indication.
'originally' suggests taking the first letters.
'cultivated' indicates an anagram.
The initial letter of 'trait' is 't'.
'cowardlinesst' with letters rearranged gives 'windsorcastle'.
'in' is the link.
(Other definitions for windsor castle that I've seen before include "Queen's residence", "royal house", "palace" and "Royal residence".)