Royal house party covered by Heat the wrong way (5)
I believe the answer is:
tudor
'royal house' is the definition.
(Tudor is an example)
'party covered by heat the wrong way' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'covered by' indicates putting letters inside.
'heat' becomes 'rut' (synonyms).
'the wrong way' says the letters should be written in reverse.
'rut' in reverse letter order is 'tur'.
'do' going inside 'tur' is 'TUDOR'.
(Other definitions for tudor that I've seen before include "Pertaining to the period 1485-1603" , "Rose" , "Style of architecture in 15th century England" , "Henry 7th's dynasty" , "Royal house of Henry VIII" .)