Force everybody to stumble (4)
I believe the answer is:
fall
'stumble' is the definition.
(fall is a kind of stumble)
'force everybody' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma**).
'everybody' becomes 'all' (I've seen this before).
'f'+'all'='FALL'
'to' acts as a link.
(Other definitions for fall that I've seen before include "Quarrel" , "Drop; autumn" , "Collapse; decline" , "Rapid descent" , "A season in Vermont?" .)