Close to the boundary of one's comprehension? (4)
I believe the answer is:
deep
'one's comprehension?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'close to the boundary' is the wordplay.
'close' becomes 'ep' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' says to put letters next to each other (I've seen this in other clues).
'the' becomes 'definite article' ('the' is the definite article in English).
'boundary' suggests removing the centre (I've seen 'boundaries' mean this (only the edge or boundary letters remain)).
'definitearticle' with its middle taken out is 'de'.
'ep' after 'de' is 'DEEP'.
'of' is the link.
Can you help me to learn more?
(Other definitions for deep that I've seen before include "greatly involved?" , "Intense -- extreme" , "down a long way" , "(Of sound) low in pitch" , "profoundly" .)