Slip up and trip (6)
I believe the answer is:
errand
'trip' is the definition.
(I know that errand is a type of trip)
'slip up and' is the wordplay.
'slip up' becomes 'err' (to err is to make an error).
'err'+'and'='ERRAND'
(Other definitions for errand that I've seen before include "A short journey to deliver orget goods" , "Short trip for a message" , "Commission, message" , "Journey to deliver message etc" , "A little job" .)