Crossword Genius

Sort of group in centre (5)

Ross

I believe the answer is:

focus

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'centre' is the definition.
(synonyms)

I don't understand how the rest of the clue works.

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(Other definitions for focus that I've seen before include "Cynosure" , "Adjust camera lenses - concentrate" , "Concentrate, zero in" , "Adjust for sharp image" , "Zoom in (on)" .)

I've seen this clue in The Sun.
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