To determine which of the given options is a revenue expenditure, it is important to understand what constitutes revenue expenditure. Revenue expenditure refers to the costs incurred for the regular operation and maintenance of a business. These expenditures are associated with current operations, and they do not result in the acquisition of a long-term asset nor do they improve the profit-making capacity of the business. Instead, they are short-term expenses that are charged to the profit and loss account in the period incurred.

Let's evaluate each option:

Overhaul expenses of a second-hand machinery purchased: This is considered a capital expenditure because it relates to an expense that improves or prolongs the life of an asset.

Legal fees to acquire a property: These fees are associated with the acquisition of a capital asset, which makes them capital expenditures.

Amount spent for replacement of worn-out portion of a machine: This is a revenue expenditure because it is a regular repair and maintenance cost that does not add to the life or value of the asset but simply keeps it in working condition.

Expenses in connection with obtaining a license for running the cinema hall: These are related to acquiring the ability to use the business (license acquisition), and hence, considered a capital expenditure.

Based on this analysis, the correct answer is the third option: Amount spent for replacement of worn-out portion of a machine. This is because it is a cost incurred for the maintenance of existing assets in their operational form, which fits the definition of revenue expenditure.