On an aeroplane with underslung wing mounted engines it is the moment created around the CofG by the thrust line of the engine....known as the thrust pitch couple.
I don't think that the CofG in relaton to Centre of lift has any bearing - this affects the force required on the tail plane to balance the moments and maintain a stable flight path.....
Hope that makes sense and is right!! ...I'm not always the best at explaining technical concepts!