Left a learner in doorway (6)
I believe the answer is:
portal
'doorway' is the definition.
(synonyms)
'left a learner' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'port'+'a'+'l'='PORTAL'
'in' acts as a link.
(Other definitions for portal that I've seen before include "'Doorway, entrance (6)'" , "Grand sort of entrance." , "Gate, entrance" , "An imposing gateway" , "Special website bringing together information from diverse sources in a uniform way" .)