The depression of French learners (4)
I believe the answer is:
dell
'the depression' is the definition.
(dell is a kind of depression)
'of french learners' is the wordplay.
'of french' becomes 'de' ('of' in French).
'learners' becomes 'LL' (the abbreviation for learner driver written twice).
'de'+'ll'='DELL'
(Other definitions for dell that I've seen before include "Small secluded valley" , "Small valley; computer company" , "Small wooded hollow or valley" , "Deep hollow or small valley" , "Dingle" .)