The most common and most likely answer to this crossword clue is the 9 letter word SYNODICAL
I've seen this crossword clue in The Times
S
Y
N
O
D
I
C
A
L
Buddy explains!

The straight part
We know that "form of council" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of council = synodical.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SYNODICAL mean?
SYNODICAL adjective- Synodic