Very happy, now the train is moving out (7)

I believe the answer is:

radiant

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'very happy' is the definition.
'radiant' can be an answer for 'happy' (thesaurus). I'm not sure about the 'very' bit.

'now the train is moving out' is the wordplay.
'now' becomes 'ad' (AD, Anno Domini, as opposed to BC, Before Christ).
'is moving' indicates anagramming the letters (letters are moved around).
'out' means one lot of letters goes inside another.
'train' with letters rearranged gives 'riant'.
'ad' put into 'riant' is 'RADIANT'.

Can you help me to learn more?

(Other definitions for radiant that I've seen before include "Lit up" , "Luminous" , "Shining - happy" , "Shining; joyful" , "Beautiful" .)

I've seen this clue in the Evening Standard.

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