Stumbled over a bloke (5)
I believe the answer is:
fella
'bloke' is the definition.
(I've seen this before)
'stumbled over a' is the wordplay.
'stumbled' becomes 'fell'.
'over' is a charade indicator (letters next to each other).
'fell'+'a'='FELLA'
(Other definitions for fella that I've seen before include "Guy" , "Chap" , "Bloke" .)