Celebration taking in a show (6)
I believe the answer is:
reveal
'show' is the definition.
(I know that reveal is a more specific form of the action show)
'celebration taking in a' is the wordplay.
I cannot really understand how this works, but
'a' is present in the answer.
'celebration' could be 'revel' (revel is a kind of celebration) and 'revel' is found within the leftover letters.
No letters remain.
This explanation may well be incorrect...
(Other definitions for reveal that I've seen before include "'Disclose, divulge (6)'" , "Make known or visible" , "'Make known, disclose (6)'" , "Expose or display" , "Make known, expose" .)