Said to be due to Calvin being noble (5)
I believe the answer is:
ducal
'being noble' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ducal that I've seen before include "Relating to the highest British hereditary title" , "Relating to a duke" , "Relating to a noble" , "Relating to a nobleman" , "of Wellington?" .)