Roman statesman sees nets cast, all half-hidden (6)

I believe the answer is:

seneca

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'roman statesman' is the definition.
(I know that Seneca is a Statesman)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for seneca that I've seen before include "philosopher in Rome" , "American tribe, Roman philosopher" , "Old Roman philosopher making a scene" , "stoical philosopher" , "Member of an Iroquois people" .)

I've seen this clue in The Times.

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