Royal train perhaps? (7)
I believe the answer is:
retinue
This clue could be a double definition.
'royal' is the first definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'train perhaps?' is the second definition.
'retinue' can be an answer for 'train' (people following someone in a procession). I am not certain of the 'perhaps?' bit.
Can you help me to learn more?
(Other definitions for retinue that I've seen before include "Group of attendants for VIP" , "Body of retainers" , "Body of attendants" , "Group of servants with important person" , "Train; attendants" .)