Trainee left with breadwinner? (7)
I believe the answer is:
learner
'trainee' is the definition.
(I've seen this before)
'left with breadwinner?' is the wordplay.
'left' becomes 'l' (common abbreviation).
'with' says to put letters next to each other.
'breadwinner?' becomes 'earner' (a breadwinner earns money).
'l'+'earner'='LEARNER'
(Other definitions for learner that I've seen before include "One under tuition" , "Amateur" , "One gaining knowledge" , "Disciple" , "Novice driver" .)