Final answer:
The word from the paragraph that helps the reader understand the meaning of 'beseech' is 'pleaded', as both imply a humble and earnest request for something.
Step-by-step explanation:
The word from the paragraph that helps the reader understand the meaning of the underlined word 'beseech' is 'pleaded'. When they beseech someone, they are earnestly and humbly asking or pleading for something. In the context of the sentence, the mouse is pleading with the lion for mercy, which aligns with the act of beseeching.