Button done on the outside, silk finally threaded through eyelet casually (6,3)

'button' is the definition.
(I know that delete key is a computer key)

'outside silk finally threaded through eyelet casually' is the wordplay.
'outside' indicates putting letters inside (some letters go outside others).
'finally' says to take the final letters.
'threaded' becomes 'de' (I can't justify this - if you can you should give a lot more credence to this answer).
'through' is an insertion indicator (inserted letters go through the word).
'casually' indicates an anagram (a casual or disordered version of the letters).
The last letter of 'silk' is 'k'.
'eyelet' with letters rearranged gives 'leteey'.
'de' going within 'leteey' is 'deleteey'.
'k' placed within 'deleteey' is 'DELETE KEY'.

'done on the' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?