Fellow coming back to give silent assent (3)
I believe the answer is:
nod
'give silent assent' is the definition.
(I've seen this in another clue)
'fellow coming back' is the wordplay.
'fellow' becomes 'don' (both can mean an academic).
'coming back' shows that the letters should be reversed in order.
'don' backwards is 'NOD'.
'to' acts as a link.
(Other definitions for nod that I've seen before include "Cain left Eden for the Land of . . ." , "Asleep in the land" , "Move head in agreement" , "Acknowledge by gesture" , "The Land of ... lay east of Eden" .)