Retired lecturer gives approval (3)
I believe the answer is:
nod
'approval' is the definition.
(I've seen this before)
'retired lecturer' is the wordplay.
'retired' says the letters should be written in reverse.
'lecturer' becomes 'don' (don can mean an academic).
'don' back-to-front is 'NOD'.
'gives' is the link.
(Other definitions for nod that I've seen before include "Bob the head" , "Fellow that's set up number 500" , "It's said to be as good as a wink" , "Indicate assent; make slip" , "Drop the head" .)