[Clipper]

It adds to the Run Away bonus or penalty of the Steed. If the Steed now has a bonus or penalty, it will replace that of your character.

Now, if you had a Turtle Steed (normally -1 to Run Away) with Press-On Wings... I don't know if the resultant +0 to Run Away is considered a bonus or not... That will likely need official clarification, although I'd go with it not having a bonus or penalty, so it doesn't replace any your character has. That provides consistency with rulings like the Boomdagger (listed as 0 Hands) not being an Item that uses Hands, but I could very well be wrong...