The present disclosure provides a composition. The composition includes (i) an ethylene-based polymer; (ii) an organic peroxide, (iii) a triorganoaminophosphine, and (iv) a protic acid-source compound (“PASC”) selected from a protic acid, a protic acid-generator compound (“PAGC”), and combinations thereof. The present disclosure also provides a coated conductor. The coated conductor includes a conductor and a coating on the conductor, the coating containing a composition including (i) an ethylene-based polymer; (ii) an organic peroxide, (iii) a triorganoaminophosphine, and (iv) a protic acid-source compound (“PASC”) selected from a protic acid, a protic acid-generator compound (“PAGC”), and combinations thereof.