Rubbish student lacking ambition (5)
I believe the answer is:
drive
'ambition' is the definition.
(I've seen this before)
'rubbish student lacking' is the wordplay.
I cannot really see how this works, but
'student' could be 'dr' (Dr is an example) and 'dr' is found within the answer.
The remaining letters 'ive' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for drive that I've seen before include "first shot" , "Chauffeur -- force" , "Force into action, impel" , "Propel or compel" , "Motor < car storage space" .)