Scots lad drinking gallon to establish connection (3,2)
I believe the answer is:
log on
'establish connection' is the definition.
I know nothing about this answer so I can't tell whether this works.
'scots lad drinking gallon' is the wordplay.
'scots lad' becomes 'loon' (I can't explain this - if you can you should give a lot more credence to this answer).
'drinking' indicates putting letters inside (inserted letters are consumed or drunk).
'gallon' becomes 'g' (abbreviation for the unit of liquid).
'loon' going around 'g' is 'LOG-ON'.
'to' is the link.
Can you help me to learn more?
(Other definitions for log on that I've seen before include "Enter a computer" , "Sign in to a computer" , "Access the Internet" , "what the lumberjack's lorry may have?" , "access network" .)