Figure in geometry, German expert brought over in care of academic (7)
I believe the answer is:
decagon
'figure in geometry' is the definition.
(type of geometric figure)
'german expert brought over in care of academic' is the wordplay.
'german' becomes 'g' (abbreviation).
'expert' becomes 'ace' (ace can informally mean very good).
'brought over' is a reversal indicator.
'in care of' indicates putting letters inside.
'academic' becomes 'don' (type of academic - especially at Oxbridge).
'g'+'ace'='gace'
'gace' back-to-front is 'ecag'.
'ecag' put within 'don' is 'DECAGON'.
(Other definitions for decagon that I've seen before include "Ten-sided plane figure" , "Plane shape" , "10-sided figure" , "Ten-sided shape" , "Go, dance on geometric figure with ten sides" .)