Clive was a DHARMA Initiative constructor in the late 1970's. He may have been killed along with other members of the DHARMA Initiative in the Purge, or he may have left the island sometime between 1977 and the Purge.
On the Island
Clive was present at "the vote" to determine if Sayid should be executed. He pulled out fire hoses to put out a fire with Juliet when a flaming DHARMA van crashed into a house at the Barracks. ("He's Our You")