A blotch leaf-mine in Salix. Possibly Aulagromyza tridentata.
No interactions present.
A mine, or surface grazing? No frass, no contents, no impression of depth.
Did you turn the leaf over, or hold it up so you could see through it? A tridentata is pretty much associated with the smooth leaved willows rather than sallows. Your leaf has almost certainly been grazed rather than mined.
Lat/Lng: 55.4737, -3.2026
OS grid ref: NT240206