Taken to the door, had looked through it when open (4,3)

'taken to the door' is the definition.
I know nothing about this answer so I can't tell whether this works.

'looked through it when open' is the wordplay.
'looked through' becomes 'snout' (I can't justify this - if you can you should give a lot more credence to this answer).
'it' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'when' becomes 'e' (I've seen this in other clues).
'open' is an insertion indicator (some letters open a gap in others).
'e'+'e'='ee'
'snout' going around 'ee' is 'SEEN OUT'.

'had' is the link.

Can you help me to learn more?