Just what's needed by a space visitor hiding in a copse (3,6)

'just what's needed' is the definition.
I can't tell whether this defines the answer.

'a space visitor hiding in a copse' is the wordplay.
'a space visitor' becomes 'et' (I can't explain this - if you can you should give a lot more credence to this answer).
'hiding in' means one lot of letters goes inside another.
'a copse' becomes 'thicket' (synonyms).
'et' put within 'thicket' is 'THE TICKET'.

'by' acts as a link.

Can you help me to learn more?