China decoded sequence (5)
I believe the answer is:
chain
'sequence' is the definition.
(I've seen this before)
'china decoded' is the wordplay.
'decoded' indicates an anagram.
'china' with letters rearranged gives 'CHAIN'.
(Other definitions for chain that I've seen before include "Event series" , "Coupling" , "Twenty-two yards" , "Series of links; sixty six feet" , "a number of hotels" .)