Partnership formed for Gallic dances inside (8)
I believe the answer is:
alliance
'partnership' is the definition.
(I've seen this before)
'gallic dances inside' is the wordplay.
'gallic' becomes 'alli' (I can't explain this - if you can you should give a lot more credence to this answer).
'inside' means to look at the middle letters.
The middle of 'dances' is 'ance'.
'alli'+'ance'='ALLIANCE'
'formed for' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for alliance that I've seen before include "Union for mutual benefit" , "League - treaty" , "The joining by political agreement or treaty" , "Confederation" , "Kind of partnership with canaille" .)