Attend lessons having boring content (7)
I believe the answer is:
endless
'boring content' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?
'attend lessons having' is the wordplay.
'having' says the answer is hidden in the clue.
'ENDLESS' is hidden in the letters of 'attend lessons'.
Can you help me to learn more?
(Other definitions for endless that I've seen before include "Everlasting" , "permanent" , "Sister of Aaron (Exodus)" , "Potentially boring" , "Occurring so frequently so as to seem uninterrupted" .)