The above sentence comes from "Mencius" and is an example sentence in a section of "Du's Handbook" that says, "The 之爲 (지위) construction is often used in combination with 惟 (유) / 唯 (유) in order to expose the object for emphatic effect. 之爲 has a syntactical function, but no separate semantic meaning when used in this way,...."使弈秋誨二人弈, 其一人專心致志, 惟弈秋之爲聽.“Supposing Chess Qiu was teaching two people to play chess and one of them was totally dedicated and only listened to Chess Qiu….”
In other words, "Du's Handbook" is saying that the 之爲 (지위) combination is used to show that the object of a verb has been moved from its place after the verb to the front of the verb for emphasis, and it also says that it does not need to be translated since it is only acting as the object marker. Well, to me, 之爲 seems like a strange marker, so I would like to suggest the following translation:
First, 弈 (혁) is the Chinese character for the Asian game "Go," which is called "paduk" (바둑) in Korean. Though it is somewhat confusing, 弈秋 (혁추) was the name of a famous Chinese "paduk" player during the time of Mencius. 弈 was his family name, which is interesting since it just happens to be the same character used for the name of the game for which he was famous.使弈秋誨二人弈, 其一人專心致志, 惟弈秋之爲聽.Supposing (使) Yí Qui (弈秋) teaches (誨) two (二) people (人) “paduk” (弈)，[and] one of them (其一人) is focused (專心) [and] devoted (致志) [and] only (惟) Yí Qiu’s actions (弈秋之爲) observes (聽).
Second, even though 之爲 (지위) does seem to act as a marker for objects moved to the front of verbs, I think it should be translated, so I translated 之 as the possessive marker and 爲 as "actions," which in Korean is 행위 (行爲) and can also mean "conduct" or "behavior." Therefore, 弈秋之爲 (혁추지위) can be translated as "Yi Qiu's actions" or "the actions of Yi Qiu."
Third, even though 聽 (청) means "to hear," my Korean dictionary says that it can also mean 살피다, which means "to watch" or "to inspect closely." Therefore, since "watching Mr. Yi's actions" sounds better than "hearing his actions," I chose to translate 聽 as "to watch" or "to observe." Besides, how do you learn to play "paduk"? One important way is to watch others play.
Finally, here is my translation of the passage from which the sentence came:
今夫弈之爲數小數也. 不專心致志則不得也.弈秋通國之善弈者也. 使弈秋誨二人弈, 其一人專心致志, 惟弈秋之爲聽. 一人雖聽之 一心以爲有鴻鵠將至, 思援弓繳而射之, 雖與之俱學, 弗若之矣.爲是其智弗若與? 曰非然也.These days (今夫), the number or “paduk” players (弈之爲數) are few (小數也). Without (不) concentration (專心) [and] devotion (致志), then (則) [the skill] cannot (不) be achieved (得也).Yí Qiu (弈秋 - 혁추) [is] the country’s (通國之) best (善) “paduk” player (弈者也). Supposing (使) Yí Qui (弈秋) teaches (誨) two (二) people (人) “paduk” (弈)，[and] one of them (其一人) is focused (專心) [and] devoted (致志) [and] only (惟) Yí Qiu’s actions (弈秋之爲) observes (聽). The other person (一人), even though (雖) [he] observes (聽) them (之), [his] whole (一) mind (心) is thinking of (以爲) a (有) wild goose (鴻) [or] swan (鵠) that is about to (將) arrive (至) [and] is imagining (思) drawing back (援) a bow (弓) string (繳) and (而) shooting (射) it (之). Although (雖) with (與) the other (지) [he] together (俱) studies (學), [he] is not (弗) the same as (若) him (之矣).
[If he] does (爲) this (是), is his (其) wisdom (智) not the same as the other (弗若與)? [I] say (曰) [it] is not (非) so (然也).