1) A verb said to mean to glean, pick or gather (OED).
In the examples quoted here the grain was being sorted, a meaning that corresponds to the OED reference of 1703, attributed to the Yorkshire diarist Thoresby: 1580 Item payd at Stockeld the same daye for bering & leasing sede wheat iiijs xd
1619 New wheat leazed and threshed 42 stowks, Brandsby
1642 the charges he shalbe att for and aboute the leasinge, thrashing, wyneinge ... the same corne, Shipton
1665-6 in the latter end of harvest last [they] were leesing Rye togeather, Hatfield Woodhouse.
2) Used of pasture land, but difficult to separate from the plural of 'lea' and 'ley ground'.
1398-9 'the farm of the pasture called les leeghes', Acaster Selby
1576 all such … landes leyes meddowes … in Slawghthwayte
1618 turned the gelding lowse in my Cow leaze where he ought not to goe, Brandsby
1668 they present Valentine Cletherow for putting his Sheepe into the leyes before they were common, Bridlington. It may be the element in minor names such as Woodsome Lees: 1566 Edmundus Brodeheade off Lees ultra Wodsom sepult, Almondbury. See EPNE11,18.