Assume you'll lose your footing because of (4,2)
I believe the answer is:
'assume' is the definition.
(I know that slip on is a more specific form of the action assume)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for slip on that I've seen before include "Type of garment" , "shoe, perhaps" , "easy to cope with when dressing" .)