Every one entering bar is willing to learn (9)
I believe the answer is:
'willing to learn' is the definition.
(willing to be taught)
'every one entering bar' is the wordplay.
'every' becomes 'each' (synonyms).
'one entering' means one lot of letters goes inside another.
'bar' becomes 'table' (the bar is a counter or table in a pub).
'each' inserted into 'table' is 'TEACHABLE'.
'is' is the link.
(Other definitions for teachable that I've seen before include "head's description of promising pupils", "interested in education", "ready to educate", "Ready and willing to be taught", "ready for education".)