Jostles (5)
(Other definitions for bumps that I've seen before include "Bulges" , "Jolts" , "birthday routine" , "Small protuberances; knocks lightly into" , "Annual treat, maybe" .)
'jostles' is the definition.
(elbowing is a kind of jostling)
This is the entire clue.
(Other definitions for elbows that I've seen before include "Bend them and have a few drink" , "Human joints" , "Nudges" , "Benders" , "Arm-joints" .)