Yorkshire for “Sile the milk, etc.” —i.e. strain it, or skim it. A sile is a sieve or strainer.
“Take a handeful of sauge, and stampe it, and temper it with hate ale, and sythene syle it thorowe a hate clothe.” —M.S. Lincoln. A i. 17 f 281
“Drink the licoure siled thorgh a clothe.” —MS. in Mr. Pettigrew's possession (fifteenth century).