Regarding a king's dynasty covering years and years (7)
I believe the answer is:
leonine
'regarding' is the definition.
Although both the answer and definition are adjectives, I cannot understand how they can define each other.
'a king's dynasty covering years and years' is the wordplay.
'a king's dynasty' becomes 'line' (I can't explain this - if you can you should give a lot more credence to this answer).
'covering' means one lot of letters goes inside another.
'years and years' becomes 'eon' (I've seen this in another clue).
'line' enclosing 'eon' is 'LEONINE'.
Can you help me to learn more?
(Other definitions for leonine that I've seen before include "about a big beast" , "Relating to a carnivore or to certain popes" , "Lion-like" , "Unusually courageous" , "Descriptive of pride" .)