Hence the classic slogan, If you find a better whisky, buy it.
这个句子是省略句吗？省略了哪部分?
Hence the classic slogan, If you find a better whisky, buy it.
hence为连接性副词，表示一种因果关系。即前面一句话的内容为后面一句话是什么原因，或者说本句是前一句话的结果。本句是个省略句，省略了 there is.
Hence there is the classic slogan, if you find a better whisky, buy it. 引号内的句子为slogan的同位语。