Weird trio accompanying king sitting on a carriage (6)
I believe the answer is:
troika
'carriage' is the definition.
(I have seen 'Russian carriage ' mean 'troika' so perhaps 'carriage' could also mean 'troika')
'weird trio accompanying king sitting on a' is the wordplay.
'weird' indicates anagramming the letters.
'accompanying' says to put letters next to each other.
'king' becomes 'k'.
'sitting on' means one lot of letters go next to another.
'trio' anagrammed gives 'troi'.
'troi'+'k'+'a'='TROIKA'
(Other definitions for troika that I've seen before include "Russian three-horse carriage" , "cart" , "Team of three" , "Russian horse-drawn vehicle" , "Russian three-horse coach" .)