Seeking nourishment, they go to ground (5)

I believe the answer is:

roots

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'seeking nourishment they' is the definition.
The definition suggests a plural noun which matches the answer.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for roots that I've seen before include "eg Parsnips" , "background" , "Cultural origin" , "Nerve endings" , "To find ancestry" .)

I've seen this clue in the Evening Standard.

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