Explanation:
* Elliptical clause: This refers to a clause where some words are omitted but understood from context.
* Adverb clause: This is a clause that modifies a verb, adjective, or adverb.
* Understood words: In this case, the understood words are "though I was".
The complete sentence, with the understood words, would be: "Though I was tired, I continued working." The words "though I was" are omitted but understood, making the adverb clause elliptical.