If the percussion is short sharp peaks (i.e. drums) well above the level of everything else you migh be able to cut it back with a limiter or a compressor with fast attack and release times. It won't know the difference between drums and anything else, but it will cut down the level of whatever's above its threshold. Obviously you'll have to experiment with the threshold and compression ratio to get the best compromise between reducing the drums and squashing the whole mix to hell and back.

Just EQ (frequency sensitive filtering) won't help much, unless there's excessive noise in a particular frequency range - bass drum, or cymbal/tambourine sizzle, on maybe a very resonant peak in the mid range that you can tune out with a notch filter.

Multiband compression as used by mastering processors might help...
It's really an impossible question to answer without hearing the problem track!

Anahata