Donald Junior perhaps - a potential presidential candidate with grassroots support (9,3)
I believe the answer is:
favourite son
'support' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'donald junior perhaps a potential presidential candidate with grassroots' is the wordplay.
I cannot quite see how this works, but
'junior' could be 'son' and 'son' is located in the answer.
'a' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for favourite son that I've seen is " Politician with grassroots support".)