Extremists bury fortune accidentally (2,6)

I believe the answer is:

by chance

'accidentally' is the definition.
(synonyms)

'extremists bury fortune' is the wordplay.
'extremists' suggests removing the centre.
'fortune' becomes 'chance' (synonyms).
'bury' with its centre taken out is 'by'.
'by'+'chance'='BY CHANCE'

(Other definitions for by chance that I've seen before include "Fortuitously" , "As it happened, without being planned" , "unwittingly" , "Accidentally, not planned" , "Without advance planning" .)

I've seen this clue in the Sydney Morning Herald.

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