Old poet turning over note respecting union (7)
I believe the answer is:
marital
'old' is the definition.
Although both the answer and definition are adjectives, I can't see how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for marital that I've seen before include "Relating to union of husband and wife" , "to do with couple's relationship" , "Of the nature of marriage" , "to do with life together" , "Of nuptials" .)