Everybody's first cheers? (3,3,4)
I believe the answer is:
all the best
'cheers?' is the definition.
(I've seen this before)
'everybody's first' is the wordplay.
'everybody' becomes 'all' (I've seen this before).
'first' becomes 'thebest'.
'all'+'thebest'='ALL THE BEST'
(Other definitions for all the best that I've seen before include "A greeting" , "every member of the elite?" , "Pick of the bunch" , "needing good luck!" , "flower, every bit of it?" .)