Scatter, climbing over duke's house (5)
I believe the answer is:
tudor
'house' is the definition.
(royal house)
'scatter climbing over duke's' is the wordplay.
'scatter' becomes 'rout' (I've seen this in another clue).
'climbing' says the letters should be written in reverse (in a down clue, letters climb up).
'over' means one lot of letters goes inside another.
'duke' becomes 'd' (abbreviation).
'rout' back-to-front is 'tuor'.
'tuor' going around 'd' is 'TUDOR'.
(Other definitions for tudor that I've seen before include "Name of the English royal family of Elizabeth 1st" , "Relating to the English ruling family in the 1500s" , "A royal house of England" , "Pre-Stuart royal house" , "Style of architecture in 15th century England" .)