为之一振 is a fixed four-character expression meaning 'to feel a sudden surge of energy or optimism (because of something)'. The character 为 is pronounced wèi in standard usage (meaning 'because of'), though the dictionary input shows wéi. This phrase is often used as a predicate complement after a motivational event, good news, or an impressive performance. It carries a literary or formal register and is common in written Chinese and news reporting. You can use it in the pattern '令/让人∼' or after a clause describing the cause.