One of the sights to take in? (7,8)
I believe the answer is:
optical illusion
'take in?' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'one of the sights' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'of' could be 'o' and 'o' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for optical illusion that I've seen before include "Something deceiving the eye" , "outwardly deceptive" , "One can't really see it" , "It's not what it seems!" , "trick" .)