Hunt ruby for one wearing crown (7)
I believe the answer is:
predate
'hunt' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how they can define each other.
'ruby for one wearing crown' is the wordplay.
'ruby for one' becomes 'red' (ruby is a kind of red).
'wearing' indicates putting letters inside.
'crown' becomes 'pate' (both can mean a person's head).
'red' put into 'pate' is 'PREDATE'.
Can you help me to learn more?
(Other definitions for predate that I've seen before include "Go before" , "Track down and feed off" , "Be earlier in time" .)