Flash one going west helping refinement (10)

I believe the answer is:

filtration

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'refinement' is the definition.
(thesaurus)

'flash one going west helping' is the wordplay.
'flash one going west' becomes 'filt' (I can't justify this - if you can you should give a lot more credence to this answer).
'helping' becomes 'ration' (I've seen this before).
'filt'+'ration'='FILTRATION'

Can you help me to learn more?

I've seen this clue in The Telegraph.

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