Get together in Queen's returning train (7)
I believe the answer is:
retinue
'train' is the definition.
(thesaurus)
'get together in queen's returning' is the wordplay.
'get together' becomes 'unite' (uniting is a kind of getting together**).
'in' indicates putting letters inside.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'returning' shows that the letters should be reversed in order.
'unite' inserted into 'er' is 'euniter'.
'euniter' reversed gives 'RETINUE'.
(Other definitions for retinue that I've seen before include "company" , "Group around VIP" , "Figure out" , "Group of followers" , "Personal staff" .)