Responsible learner with one expert (6)
I believe the answer is:
liable
'responsible' is the definition.
(I've seen this before)
'learner with one expert' is the wordplay.
'learner' becomes 'l'.
'with' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'expert' becomes 'able' (I've seen this in other clues**).
'l'+'i'+'able'='LIABLE'
(Other definitions for liable that I've seen before include "Legally answerable" , "To blame" , "legally obliged, held responsible" , "Responsible at law" , "Subject to an obligation" .)