  We present the first cosmological measurement derived from a galaxy density
field subject to a `clipping' transformation. By enforcing an upper bound on
the galaxy number density field in the Galaxy and Mass Assembly survey (GAMA),
contributions from the nonlinear processes of virialisation and galaxy bias are
greatly reduced. This leads to a galaxy power spectrum which is easier to
model, without calibration from numerical simulations.
  We develop a theoretical model for the power spectrum of a clipped field in
redshift space, which is exact for the case of anisotropic Gaussian fields.
Clipping is found to extend the applicability of the conventional Kaiser
prescription by more than a factor of three in wavenumber, or a factor of
thirty in terms of the number of Fourier modes. By modelling the galaxy power
spectrum on scales k < 0.3 h/Mpc and density fluctuations $\delta_g < 4$ we
measure the normalised growth rate $f\sigma_8(z = 0.18) = 0.29 \pm 0.10$.
