Firmly established as England captain? (6)

I believe the answer is:

rooted

'firmly established' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for rooted that I've seen before include "Stuck in one place, like plant" , "Stuck to the spot" , "Fixed in place like plants in soil" , "Firmly established and well planted" , "Firmly established in a plantlike way" .)

I've seen this clue in The Guardian.

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