Briefly assist veteran stalked by two Celts in central Europe (8)

I believe the answer is:

helvetii

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'celts in central europe' is the definition.
The definition suggests a plural noun which matches the answer.

'briefly assist veteran stalked by two' is the wordplay.
'briefly' means to remove the last letter.
'assist' becomes 'help' (synonyms).
'veteran' becomes 'vet' (abbreviation).
'stalked by two' becomes 'ii' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'help' with its final letter taken off is 'hel'.
'hel'+'vet'+'ii'='HELVETII'

Can you help me to learn more?

(Another definition for helvetii that I've seen is " Celtic tribe".)

I've seen this clue in The Independent.

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