19a Cattle scour ranges of feeding-ground (4) R_NS so no doubt RUNS is the answer, and one definition of RUN is "range of feeding ground", but where does "cattle scour" come into it?
verb intransitive to scrub and polish; to serve or act as a purgative; (of livestock) to have diarrhoea.
noun the action, place, or means of scouring; diarrhoea in cattle,