arXiv:2610.32133v1 Announce Type: cross Abstract: Target speaker extraction (TSE) aims to extract a desired speaker from a mixture using auxiliary clues such as enrollment speech. An interferer-related representation can provide a useful negative clue for TSE, but such information is not directly available from the target enrollment. To derive this representation from the observed mixture, we analyze the relationship between the speaker representations of a speech mixture and its constituent speakers. Our analysis shows that the mixture centroid lies near the midpoint of its constituent speaker centroids, whereas this relationship does not hold for single-utterance embeddings. Based on this observation, we propose NECTAR, NEgative Clue for TARget speaker extraction, which automatically derives an interferer-related negative clue from the mixture using the centroid-space relationship. We further introduce a Centroid-Space Mapper (CSM) to estimate the required centroid representations from a mixture and a target enrollment. NECTAR achieves the highest SI-SDRi on Libri2Mix among the compared systems trained on LibriSpeech train-clean-100, reaching 16.18 dB.