Desire assistant to return with a little French by mid-September (8)
I believe the answer is:
appetite
'desire' is the definition.
(I know that appetite is a type of craving)
'assistant to return with a little french by mid-september' is the wordplay.
'assistant' becomes 'PA' (personal assistant).
'to return' says the letters should be written in reverse.
'with' says to put letters next to each other.
'a little french by mid-september' becomes 'petite' (I can't justify this - if you can you should give a lot more credence to this answer).
'pa' in reverse letter order is 'ap'.
'ap'+'petite'='APPETITE'
Can you help me to learn more?
(Other definitions for appetite that I've seen before include "Keenness for food" , "Hunger; desire" , "desire to take courses" , "enthusiasm" , "'Strong desire, craving (8)'" .)