Still to get back from Euston (3)
I believe the answer is:
not
'still to get back from euston' is the definition.
I can't tell whether this definition defines the answer.
'still to get back from euston' is the wordplay.
'still' becomes 'ot' (I can't justify this - if you can you should believe this answer much more).
'to get' says to put letters next to each other.
'back from' suggests the final letters (the letter at the back of the word).
The final letter of 'euston' is 'n'.
'ot' put after 'n' is 'NOT'.
Can you help me to learn more?
(Other definitions for not that I've seen before include "Word of negation" , "Ton (anag.)" , "In no way, never" , "It negates a word" , "Having close-cut hair" .)