Frank's very dry with a learner (6)
I believe the answer is:
brutal
'frank's' is the definition.
(both can mean uncomfortably direct or honest)
'very dry with a learner' is the wordplay.
'very dry' becomes 'brut' (term for very dry wine).
'with' is a charade indicator (letters next to each other).
'learner' becomes 'l'.
'brut'+'a'+'l'='BRUTAL'
(Other definitions for brutal that I've seen before include "Savagely violent" , "Senselessly cruel" , "Cruel, inhuman" , "Very cruel and beastly" , "Disposed to inflict pain" .)