This paper proposes a digital and lightweight delay-based detector against clock glitch fault injection attacks (FIAs). The injected glitch of the clock is monitored by the proposed detector with the inserted delay chain which is elaborated. The experiments on iterative DES cipher circuit verify that the detector is effective to detect the clock glitches. The incremental overhead about hardware and power is 0.058% and 4.5%, respectively. The detector also has the property against the threat of aging phenomenon.