His arguments in the debate were well-defended with solid evidence and clear logic.

well-defended 是由副词 well（好地）和动词 defend（辩护、防卫）的过去分词 defended 组成的复合形容词。defend 由前缀 de-（表示"远离"）和词根 fend（"击打"）组成，字面意思是"通过击打使远离"。 well-defended 表示"辩护得很好的"，形容论点或立场得到充分有力的支持和保护。