Inability to see approach quoted verbally by head (4-11)

'inability' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?

'see approach quoted verbally by head' is the wordplay.
I cannot really see how this works, but
'see' could be 'sight' (I've seen this before) and 'sight' is found within the answer.
'approach' could be 'near' (synonyms) and 'near' is present in the answer.
'head' could be 'ness' (ness is a headland) and 'ness' is located in the answer.
The remaining letters 'ed' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

'to' is the link.

Can you help me to learn more?