Endless delight, of course, producing riches (8)
I believe the answer is:
treasure
'riches' is the definition.
(treasure is a kind of riches)
'endless delight of course' is the wordplay.
'endless' means to remove the last letter.
'delight' becomes 'treat' (I have seen 'Special delight ' mean 'treat' so perhaps 'delight' could also mean 'treat').
'of course' becomes 'sure' (I've seen this before).
'treat' with its final letter taken away is 'trea'.
'trea'+'sure'='TREASURE'
'producing' acts as a link.
(Other definitions for treasure that I've seen before include "Highly-prize a possession" , "much-loved person" , "Wealth stored up or hidden away" , "Accumulated wealth, could be buried" , "Stored-up wealth" .)