Reading could give us unending pleasure (7)
I believe the answer is:
perusal
'reading' is the definition.
(I know that perusal is a type of reading)
'give us unending pleasure' is the wordplay.
I cannot really see how this works, but
'us' could be 'usa' (synonyms) and 'usa' is found in the answer.
This explanation may well be incorrect...
'could' is the link.
Can you help me to learn more?
(Other definitions for perusal that I've seen before include "Inspection" , "Careful look" , "Careful examination" , "Thorough reading" , "Reading, examination" .)