Final answer:
Hugh Gaitskell proposed to abandon Clause Four of the Labour Party's constitution in C) 1959, following an election defeat.
Step-by-step explanation:
Hugh Gaitskell, as the leader of the British Labour Party, attempted to revise the direction of the party by proposing to abandon Clause Four, which was part of the party's constitution.
This clause committed the party to the nationalization of industry. Gaitskell made this attempt after the 1959 general election defeat, believing that modernizing the party's platform would make it more electable.
Therefore, the correct answer to the question of when Gaitskell tried to abandon Clause 4 is C) 1959.