Michael Jackson song climbing July charts essentially - it's to do with star association (7)
I believe the answer is:
nebular
'star association' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I can't see?
'michael jackson song climbing july charts essentially it's to do' is the wordplay.
'michael jackson song' becomes 'ben' (I've seen this in another clue).
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'july charts' becomes 'ula' (I can't explain this - if you can you should give a lot more credence to this answer).
'essentially' says to take the centre.
'it's to do' becomes 'party' (I've seen this before).
The central letter of 'party' is 'r'.
'ben' written backwards gives 'neb'.
'neb'+'ula'+'r'='NEBULAR'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for nebular that I've seen before include "Misty" , "Like clouds" , "Hazy and formless" , "Cloudlike" , "Like a cloud (in space)" .)