Express speed from Euston (3)

I believe the answer is:
ton
'express speed' is the definition.
'ton' can be an answer for 'speed' (I've seen this before). I am not certain of the 'express' bit.
'euston' is the wordplay.
'TON' is hidden in amongst the letters.
However, I'm not sure how this is indicated.
'from' is the link.
Can you help me to learn more?
(Other definitions for ton that I've seen before include "Century" , "20cwt" , "Imperial unit of weight" , "2240lbs" , "High-speed" .)
