Retinue stuck in express? (4,5)

I believe the answer is:

fast train

I'm a little stuck... Click here to teach me more about this clue!

'retinue' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'stuck in express?' is the wordplay.
'stuck' becomes 'fast' (both can mean secure).
'in express?' becomes 'train' (express is a kind of train. I am not sure about the 'in' bit.).
'fast'+'train'='FAST TRAIN'

Can you help me to learn more?

I've seen this clue in The Irish News.

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