Throughout The Great Gatsby the trope of the manipulation of time dominates the narrative: Gatsby stands on his "blue lawn" gazing longingly at the green light at the end of Daisy's pier, a signal of the possibilities of the present with the walkway to her house from the sea of the past; further, the revelation of the character and history of Gatsby himself is revealed in a non-chronological order that emphasizes his self-reinvention; songs such as "Three O'Clock in the Morning," prevail throughout the narrative evoking "romantic possibilties" and the supra-reality of the Jazz Age.
In Chapter Five, Gatsby solicits the aid of Nick as his intermediary for what he hopes will be his romantic reunion with Daisy after five years. However, in his nervousness and excitement, Gatsby acts like an awkward youth:
Gatsby, his hands still in his pockets, was reclining against the mantelpiece in a strained counterfeit of perfect ease, even of boredom. His head leaned back so that it rested against the face of a defunct mantelpiece clock and from this position his distraught eyes stared down at Daisy....
Clearly, the clock as "a death of time" is symbolic. When it falls, Gatsby tries to set it right with "trembling fingers." Nick narrates that he thought that the clock "had smashed in pieces on the floor."
Gatsby, who is haunted by time, has his first attempt at reclaiming the past is a failure. But, he has an extraordinary gift for hope and attempts to recover by later inviting Daisy to his mansion. Nevertheless, the symbolic fallen clock presages the outcome of Gatsby's great hope.
Gatsby, in his frustration and uneasiness, destroys the clock on the mantle piece. Nick tries to sheepishly explain that it was an old clock anyway. Gatsby destroying the clock is a physical manifestation of his nervousness around Daisy. Its almost an intensely comical scene because a serious event is delivered in a ridiculous tone.