Certainly may be evidenced in wrecked retina - this? (9)
I believe the answer is:
eyestrain
'certainly may be evidenced in wrecked retina this?' is the definition.
The definition suggests a singular noun which matches the answer.
'in wrecked retina this?' is the wordplay.
'in' is an insertion indicator.
'wrecked' indicates an anagram.
'this?' becomes 'yes' (I can't justify this - if you can you should give a lot more credence to this answer).
'retina' anagrammed gives 'etrain'.
'etrain' enclosing 'yes' is 'EYESTRAIN'.
Can you help me to learn more?
(Other definitions for eyestrain that I've seen before include "You're looking too hard for this" , "Vision problem" , "Optical irritation or tiredness" , "Tension on the visual organ" , "A serenity leading to ocular stress" .)