Cause to stumble (4,2)
I believe the answer is:
trip up
'cause to stumble' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for trip up that I've seen before include "Catch out or cause to stumble" , "Alpine excursion, perhaps" , "Blunder" , "fluff" , "'Cause to stumble (4,2)'" .)