Most of journey with a learner will be an ordeal (5)
I believe the answer is:
'an ordeal' is the definition.
(I've seen this before)
'most of journey with a learner' is the wordplay.
'most of' means to remove the last letter.
'journey' becomes 'trip' (trip is a kind of journey).
'with' means one lot of letters go next to another.
'learner' becomes 'l'.
'trip' with its last letter taken away is 'tri'.
'tri'+'a'+'l'='TRIAL'
'will be' is the link.
(Other definitions for trial that I've seen before include "French actor who sings", "Test of performance", "Hearing - difficulty", "Ordeal, perhaps in court", "Court proceeding".)
I've seen this clue in The Telegraph.