Number in tour round royal house (5)
I believe the answer is:
tudor
'royal house' is the definition.
(Tudor is an example)
'number in tour round' is the wordplay.
'number' becomes 'd' (D is an example).
'in' means one lot of letters goes inside another.
'round' indicates anagramming the letters.
'tour' is an anagram of 'tuor'.
'd' put into 'tuor' is 'TUDOR'.
(Other definitions for tudor that I've seen before include "English royal dynasty" , "Half-timbered-house style" , "Style of architecture in 15th century England" , "Regal family" , "Royal house of Henry VIII" .)