In a straight line (2,3,4,5)
I believe the answer is:
as the crow flies
'in a straight line' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for as the crow flies that I've seen before include "move in a straight line" , "By direct route" , "How rook moves" , "without deviating" , "taking shortest route" .)