。
The eloquent scholar graciously took part in the debate.
Literal
Eloquent-[attributive-な] that scholar [topic-は] gladly debate [to-に] participate-[inward-benefactive-してくれた].
Three pieces worth noting. 雄弁な ('eloquent') is the attributive form of 雄弁, a na-adjective modifier. 快く ('gladly, willingly') is the adverbial form of 快い ('pleasant, comfortable'). 参加してくれた uses the inward benefactive ~てくれる — 'participated for us / did the kindness of participating.' The sentence has the texture of formal event reporting.