Can’t understand why you turn a blind eye to? (4,2,3)

'can't understand why you turn' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'a blind eye to?' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'eye' could be 'see' (see is a kind of eye) and 'see' is found within the answer.
'to?' could be 'to' and 'to' is found in the answer.
The remaining letters 'fil' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?