I have been inside and no, there is no clutch at all. The slippage was due to a worn drive system.. The end of the motor shaft has a pinion, which drives crown wheel, which was partially supported on one side by a casting. The quite soft metal crown wheel had worn in one spot, which was where it was causing slipping. The crown wheel was on a spindle, with a small roller bearing top and bottom, bottom in rigid casting, top bearing supported by the plastic housing. Absolutely no adjustment anywhere at all and a very poor design.
I fitted a small washer under the bottom bearing, to push the crown wheel a tad further out of the casting, making the crown wheel a tighter fit against the motor pinion. It will not likely last long.
I have had it around three years, during which time have have probably cut our bit of hedge around nine times in total, so rather disappointed that it survived such a short time.