Upholder of Trident ban I train in movement (9)

I believe the answer is:

britannia

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'upholder of trident' is the definition.
The definition suggests a singular noun which matches the answer.

'ban i train in movement' is the wordplay.
'in movement' is an anagram indicator.
'ban'+'i'+'train'='banitrain'
'banitrain' with letters rearranged gives 'BRITANNIA'.

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(Other definitions for britannia that I've seen before include "Female warrior" , "province" , "Warrior personifying Great Britain" , "Trident-bearing figure" , "Figure on fifty pence coins" .)

I've seen this clue in The Times.

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