Study with German and let in again (7)
I believe the answer is:
readmit
'let in again' is the definition.
('admit' can be a synonym for 'let in' so perhaps 'readmit' is OK for 'let in again')
'study with german' is the wordplay.
'study' becomes 'read' (synonyms).
'with german' becomes 'mit' ('with' in German).
'read'+'mit'='READMIT'
'and' acts as a link.
(Other definitions for readmit that I've seen before include "Allow back into" , "Again accept" , "Dear Tim (anag.)" , "Take in again" , "Welcome back" .)