Select the most appropriate idiom to fill in the blank.

The festival expenses are bound to ______ in my pocket.

make a dent

The most appropriate idiom to fill in the blank is make a dent.

The idiom make a dent means to have a noticeable impact on something. In this context, it means that the festival expenses are bound to have a noticeable impact on the speaker's pocket.

The other options are incorrect.

• Be out of the blue means to happen unexpectedly. This idiom is not appropriate in this context because the festival expenses are not unexpected.
• Give a clean chit means to give someone a favorable report. This idiom is not appropriate in this context because it does not make sense to say that the festival expenses will give the speaker a favorable report.
• Be upfront means to be honest and direct. This idiom is not appropriate in this context because it does not make sense to say that the festival expenses will be honest and direct.