Single-file formation (4)
I believe the answer is:
line
(Other definitions for line that I've seen before include "Fill" , "Ancestry" , "job" , "Long narrow mark" , "An American queue" .)
I believe the answer is:
line
(Other definitions for line that I've seen before include "Fill" , "Ancestry" , "job" , "Long narrow mark" , "An American queue" .)