Maybe Henry VIII’s part you tried to discover last of all (5)
I believe the answer is:
tudor
'maybe henry viii's' is the definition.
(Henry VIII was a Tudor king)
'part you tried to discover last of all' is the wordplay.
'last of all' says to take the final letters.
The final letters of 'part you tried to discover' are 'TUDOR'.
(Other definitions for tudor that I've seen before include "Welsh royal house" , "Dynasty's founder" , "Henry 7th's dynasty" , "(Pertaining to) royal house" , "Member of the dynasty ruling England 1485-1603" .)