Slashclaw states, "If your engaged Creature has Recklessness, deal damage equal to twice its Recklessness value"
Now if say we had a Blazvatan with Reckless 25 and Conjurors such as say Ranun
Ranun states "Reduce Recklessness damage dealt to Warbeasts you control by 10"
This technically isn't reducing the recklessness... only the damage dealt from the Recklessness itself. Thus does the Slashclaw do 50 damage or less.