Bar to current beer supply? (7,8)
I believe the answer is:
draught excluder
'bar to current' is the definition.
(bar which blocks currents of cold air)
'beer supply?' is the wordplay.
'beer' becomes 'draught' (draught beer is a type of beer).
'supply?' becomes 'excluder' (I am not sure about this - if you are sure you should believe this answer much more).
'draught'+'excluder'='DRAUGHT EXCLUDER'
Can you help me to learn more?
(Other definitions for draught excluder that I've seen before include "Solution to current problem" , "that might stop delivery of beer?" , "Current bar" .)