Dog runs off at first call from umpire (4)
I believe the answer is:
over
'first call from umpire' is the definition.
I can't tell whether this definition defines the answer.
'dog runs off' is the wordplay.
'dog' becomes 'rover' (Rover is a common name for a pet dog).
'runs' becomes 'r' (cricket abbreviation).
'off' suggests deleting specific letters (some letters taken off).
'rover' with 'r' taken away is 'OVER'.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for over that I've seen before include "Finished, done" , "Past, surplus" , "Finished like round of bowling in cricket" , "Having gone < to America" , "The delivery is concluded" .)