Intelligence of supporter on good terms with current head (10)
I believe the answer is:
braininess
'intelligence of supporter' is the definition.
The definition suggests a singular noun which matches the answer.
'good terms with current head' is the wordplay.
'good terms' becomes 'brain' (I can't justify this - if you can you should give a lot more credence to this answer).
'with' says to put letters next to each other.
'current' becomes 'I' (symbol for electric current).
'head' becomes 'ness' (ness is a headland).
'brain'+'i'+'ness'='BRAININESS'
'on' is the link.
Can you help me to learn more?
(Another definition for braininess that I've seen is " intelligence needed".)