Court, I see, overcome by celebration involving many stars (8)
I believe the answer is:
galactic
'involving many stars' is the definition.
I can't tell whether this defines the answer.
'court i see overcome by celebration' is the wordplay.
'court' becomes 'ct' (abbreviation used in road names).
'see' becomes 'C' (the word for the letter, according to Chambers).
'overcome by' means one lot of letters go next to another (in a down clue, some letters go over others).
'celebration' becomes 'gala' (gala is a kind of celebration).
'ct'+'i'+'c'='ctic'
'ctic' put after 'gala' is 'GALACTIC'.
Can you help me to learn more?
(Other definitions for galactic that I've seen before include "Huge - relating to a star system" , "Relating to, eg, the Milky Way" , "Referring to the star system" , "Of large independent system of stars" , "Relating to large star systems" .)