Eyes like this seen oddly in secret (5-3)
I believe the answer is:
close-set
'eyes like this' is the definition.
The definition suggests a singular noun but the answer is not.
'seen oddly in secret' is the wordplay.
'oddly' indicates alternate letters.
'in' is an insertion indicator.
'secret' becomes 'closet' ('closet' can be a synonym of 'secret'**).
The alternating letters of 'seen' are 'se'.
'se' placed into 'closet' is 'CLOSE-SET'.
Can you help me to learn more?
(Other definitions for close-set that I've seen before include "Tight together" , "(Eg of eyes) very near to each other" , "With little space between them, eyes perhaps" .)