Question

Point out the figures of speech it is an open secret

Answer 1

The answer is: In the sentence, it is an open secret, the subject is “it”, “is” is the main verb, “an” is the indefinite article working as the determiner, and secret is the object.  

Here the word open is performing as an adjective that is qualifying the object (noun) ‘secret’.

All the words are interrelated here for offering a clear meaning of the sentence.