Clue: Don't hinder telling of legend with face pulled repeatedly by hack, ok? (4,3,2,3,3)
Answer: KEEP OUT OF THE WAY
Explanation: Definition: Don't hinder
A charade of KEE, sounding like ('telling of') KEY ('legend' to a diagram, say) plus POUT ('face pulled') plus OFT ('repeatedly') plus HEW ('hack') plus AY ('ok').