Great lover married? Good one might be bad! (7)
I believe the answer is:
antonym
'good one might be bad' is the definition.
I can't tell whether this defines the answer.
'great lover married?' is the wordplay.
'great lover' becomes 'antony' (I have seen 'Lover of Cleopatra ' mean 'antony' so perhaps 'lover' could also mean 'antony'. I am not sure about the 'great' bit.).
'married?' becomes 'm'.
'antony'+'m'='ANTONYM'
Can you help me to learn more?
(Other definitions for antonym that I've seen before include "As 'happy' is to 'sad' or 'long' to 'short'" , ""Loud" as opposed to "quiet", for example" , "A word opposite in meaning to another" , "Word that means the opposite of another" , "A word's opposite" .)