XE601 is the Hunter you refer to. Back on the air show scene until fairly recently but now (tragically) gone to France.
A&AEE operated it for a long time although I believe that it actually belonged to Porton Down for much of it's time at Boscombe Down. It certainly carried a wing pod that sprayed water for chemical simulation during exercises, but I believe it also flew tests connected with dispersion effects, as did Canberra WV787 before being used as an icing spray tanker.
Perhaps the mod details refer to the chemical dispersion tank/s that could be carried by the Hunter?