Thinks twice, then leaves a true monster (11)

I believe the answer is:

reevaluates

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'thinks' is the definition.
The answer and definition can be both related to thinking as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

'twice then leaves a true monster' is the wordplay.
'leaves a true' anagrams to 'REEVALUATES'.
Though, I'm not clear how the anagram is indicated.

Can you help me to learn more?

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

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