We study the performance of a two-hop full-duplex OFDM relay link, where the relay, or in-band repeater, amplifies and forwards its input signal on the same channel as the main transmitter. We derive new closed-form expressions for the end-to-end signal-to-interference and noise ratio (SINR) when the multipath channels are modeled with clustered exponential power-delay profiles. Our system model incorporates the deleterious effect of loop interference associated with full-duplex relays due to signal leakage from transmission to reception. In particular, our analysis shows that the relay gain is a central parameter in the mitigation of residual loop interference and for the optimization of the end-to-end performance.