Not all WWI service records have survived; in fact a lot of them have not.
ASC = Army Service Corps.
If you can post up his name we could search for any records that are available.
Wikipedia has a page about the 11th (Northern) Division - see link below. It includes mention of
Divisional Transport: 11th Divisional Train, Army Service Corps (ASC) – remained in England when division went to Gallipoli; later joined 26th Division in Salonika - 112th, 113th, 114th 115th Companies, ASC
https://en.wikipedia.org/wiki/11th_(Northern)_Division