Think it’s in the main true, but garbled (8)

I believe the answer is:

ruminate

I'm a little stuck... Click here to teach me more about this clue!

'think' is the definition.
(I know that ruminate is a more specific form of the action the think)

'in the main true but garbled' is the wordplay.
'main true' can be anagrammed to 'RUMINATE'.
But, I am unsure how the anagram is indicated.

'it's' is the link.

Can you help me to learn more?

(Other definitions for ruminate that I've seen before include "Chew - ponder" , "Ponder or meditate in mature way" , "'Reflect deeply, chew the cud (8)'" , "deliberate" , "Think over - as cows do?" .)

I've seen this clue in the Evening Standard.

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