Lays open the topics (8)

I believe the answer is:

subjects

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'the topics' is the definition.
('subject' can be a synonym of 'topic')

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for subjects that I've seen before include "things to discuss" , "They owe allegiance to a monarch" , "Cubs jest about themes or subordinates" , "Monarchs have these" , "Topics or vassals" .)

I've seen this clue in The Everyman puzzle in The Observer.

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