Economist endlessly goes over old time that is critical (7)
I believe the answer is:
keynote
'economist endlessly goes over old time that is critical' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'economist endlessly goes over old time' is the wordplay.
'economist' becomes 'keynes' (Keynes is an example).
'endlessly' means to remove the last letter.
'goes over' indicates putting letters inside (to go over can mean to wrap around).
'old time' becomes 'ot' (this might be a standard abbreviation which I don't know about).
'keynes' with its final letter removed is 'keyne'.
'keyne' enclosing 'ot' is 'KEYNOTE'.
Can you help me to learn more?
(Other definitions for keynote that I've seen before include "Speech that sets the tone of a conference" , "Gist" , "Principal theme (eg of a speech)" , "Main theme - tonic" , "of fundamental importance" .)