The problem of radar detection in compound Gaussian clutter when a radar signature is not completely known has not been considered yet and is addressed in this paper. We proposed a robust technique to detect, based on the generalized likelihood ratio test, a point-like target embedded in compound Gaussian clutter. Employing an array of antennas, we assume that the actual steering vector departs from the nominal one, but lies in a known interval. The detection is then secured by employing a semi-definite programming. It is confirmed via simulation that the proposed detector experiences a negligible detection loss compared to an adaptive normalized matched filter in a perfectly matched case, but outperforms in cases of mismatched signal. Remarkably, the proposed detector possesses constant false alarm rate with respect to the clutter covariance matrix.