[Drinking] Buying a beer for a mate who's running late.....

[FamilyGuy]

Regular event in the days of pints being cheaper.
It would be 'bin' or 'pipes' but always shoved one in if first in the pub for a nights drinking.

Yeh, "leave one in the pipe for John" was a frequent request when I frequented the Red Lion in Turners Hill

 

[Arthur]

Another vote for standard.

As others have said saying left one in the wood/bin very common round my way.

 

[schmunk]

Never heard of it, or indeed the practice of buying a drink and not having it served immediately...