Duke in defeat sent up royal house (5)
I believe the answer is:
tudor
'royal house' is the definition.
(Tudor is an example)
'duke in defeat sent up' is the wordplay.
'duke' becomes 'd' (abbreviation).
'in' means one lot of letters goes inside another.
'defeat' becomes 'rout' (rout is a kind of defeat).
'sent up' says the letters should be written in reverse.
'd' placed into 'rout' is 'rodut'.
'rodut' in reverse letter order is 'TUDOR'.
(Other definitions for tudor that I've seen before include "Rose" , "Welsh royal family" , "Name of a royal house" , "Member of royal family" , "Former English royal house" .)