Dropped the ball (7)
'dropped the ball' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for erred that I've seen before include "Went wrong" , "was inaccurate" , "Made mistake, was incorrect" , "Made a mistake, was wrong" , "Went astray" .)
(Other definitions for fumbled that I've seen before include "Perhaps failed to catch" , "Handled awkwardly, groped about" , "Mishandled" , "Fourteen-line poem" .)