Stumbled (7)
'stumbled' is the definition.
('trip' can be a synonym of 'stumble')
This is the entire clue.
(Other definitions for tripped that I've seen before include "Missed a step, stumbled" , "Came a cropper" , "Took acid" .)
(Other definitions for staggered that I've seen before include "Arranged to take place at intervals" , "not to be starting together" , "Lurched, reeled" , "Amazed" , "Did floor" .)