A yellow jacket you slipped on? (6,4)
I believe the answer is:
banana skin
'you slipped on?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'a yellow jacket' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
'jacket' could be 'ski' (ski jacket is a kind of jacket) and 'ski' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for banana skin that I've seen before include "Potential source of slip-up" , "Something causing downfall (colloq.)" , "One to slip on" , "something to cause embarrassment" , "Potential for accident, embarrassment" .)