It just means to make your grips more sticky or grippy. If you find that your grips have gone quite shiny and slippy then you end up gripping them tighter...fatal for your golf swing. You end up inhibiting your natural wrist cock and swinging stiffly and without any "flow". You'll lose a heap of distance and control. Seve used to say that you should grip the club with the same tightness you would if you were holding a small bird in your hand.
The best thing to do is rub your grips down with a towel and hot, soapy water. Or even better, get your slippiest clubs re-gripped. I re-grip my most used clubs, my wedges, once a year. Nevada Bob's do each club, including fitting, which only takes 2 minutes, for Â£3 in my area so it doesn't cost the earth. Hope this helps.
Viscount, I'm not sure that Seve meant all shots. If I did then maybe I wouldn't be playing off 9! However, it does make a great difference to my driving distance when I soften the grip pressure and let the swing flow freely.