Clamhand is a slur used to describe Whites in a derogatory way. Probably used because many white males used to live in poverty, surviving by scavenging clams and the like.
The word Clamhand is a racial slur that has been used historically to degrade and dehumanize whites. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to whites. If you are unsure about whether or not it is appropriate to use the word Clamhand, it is best to err on the side of caution and avoid using it in any situation.