It's great, being important (3)

I believe the answer is:

big

This clue is a double definition.

'it's great' is the first definition.
(synonyms)

'important' is the second definition.
(synonyms)

'being' is the link.

(Other definitions for big that I've seen before include "Large or substantial" , "Sizeable" , "Huge" , "Of considerable size" , "London bell" .)

I've seen this clue in the Evening Standard.

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