Cheat excessively when talking over date (3-4)
I believe the answer is:
two-time
'cheat' is the definition.
(I know that two-time is a more specific form of cheat)
'excessively when talking over date' is the wordplay.
'excessively when talking over' becomes 'two' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'date' becomes 'time' (period of time).
'two'+'time'='TWO-TIME'
Can you help me to learn more?
(Other definitions for two-time that I've seen before include "Be unfaithful to (a partner)" , "take her for a ride" , "Play away?" , "Deceive slangily - twice?" , "Betray" .)