Sentence:  "At 1057 we were just over the islands and at 1100 the tail gunner reported flak at six <WSD>o'clock</WSD>, below." 
Meaning of the word marked with <WSD> tags:  In conjunction with a numeral, indicates the direction, relative to the speaker or a vehicle, especially an aircraft, corresponding to the direction the hour hand is pointing at the time corresponding to the numeral, with twelve representing directly ahead and three being to the right.