Communist is concealed? Must be unearthed again (12)

I believe the answer is:

rediscovered

'unearthed again' is the definition.
(discovered again)

'communist is concealed?' is the wordplay.
'communist' becomes 'red' (red can informally mean communist).
'concealed?' becomes 'covered' (covering is a kind of concealing).
'red'+'is'+'covered'='REDISCOVERED'

'must be' is the link.

(Another definition for rediscovered that I've seen is " Again found".)

I've seen this clue in The Times.

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