David Cassidy recorded an extended live version for his 1974 album Cassidy Live! (Bell Records, UK # 9; recorded live in Great Britain in May 1974). The track features extensive and complex lead-guitar solos by Cassidy himself. The album received rave reviews. Critic Dave Thompson wrote for Allmusic, "Recorded live on his 1974 world tour, at the height (and, though nobody knew it, in the final days) of Cassidy-mania, Cassidy Live is a peculiar document, on the one hand standing as an indication of just how fierce the hysteria around the lad was, but, on the other, living proof of what a sensational showman he was; as evidenced by tracks like' For What It's Worth'." He concluded, "Rock history has sidelined Cassidy with a finality that seems almost personal, shovelling him up a teen idol side street from which the only escape was retirement and resignation. Cassidy Live, however, was recorded while he still thought he had a chance of advancing -- and few period live albums come even close to capturing its excitement."

Answer this question: who played lead guitar on for what it's worth? Let's think fast. Stream of consciousness:
The important part for answering this question is: The track features extensive and complex lead-guitar solos by Cassidy himself. So the final answer is David Cassidy.