Starry celebration given by commander-in-chief? About time (8)
I believe the answer is:
galactic
'starry' is the definition.
(like a galaxy)
'celebration given by commander-in-chief? about time' is the wordplay.
'celebration' becomes 'gala' (gala is a kind of celebration).
'given by' means one lot of letters go next to another.
'commander-in-chief?' becomes 'cic'.
'about' is an insertion indicator.
'time' becomes 't' (abbreviation).
'cic' placed around 't' is 'ctic'.
'gala'+'ctic'='GALACTIC'
(Other definitions for galactic that I've seen before include "Huge - relating to a star system" , "To do with large independent systems of stars" , "More than stellar" , "Relating to large star systems" , "Referring to the star system" .)