First of challenges that hurt King Edward, say -- lazybones! (5,6)
I believe the answer is:
couch potato
'lazybones' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'first of challenges that hurt king edward say' is the wordplay.
'first of challenges' becomes 'c' (1st letter of 'challenges').
'that hurt' becomes 'ouch' (expression of pain).
'king edward say' becomes 'potato' (King Edward is a type of potato).
'c'+'ouch'+'potato'='COUCH POTATO'
Can you help me to learn more?
(Other definitions for couch potato that I've seen before include "Layabout" , "one watching TV till late?" , "Habitual TV watcher" , "Inveterate TV-watcher" , "A continual watcher of TV, videos, etc" .)