The sentence provided is: She loves to play the piano in her free time. In order to determine the part of speech for the underlined word "loves," it is important to understand its function within the sentence.
A verb is a word that describes an action, state, or occurrence. In this sentence, "loves" is used to express an action or feeling that the subject, 'She,' performs. The action being described is the feeling of love toward playing the piano.
Since "loves" is indicating what 'She' does, it functions as a verb.
Therefore, the correct classification for the underlined word "loves" is a verb.