Set the ball rolling! Good luck (3,3,4)
I believe the answer is:
all the best
'good luck' is the definition.
(I've seen this before)
'set the ball rolling' is the wordplay.
'rolling' is an anagram indicator.
'set'+'the'+'ball'='settheball'
'settheball' with letters rearranged gives 'ALL THE BEST'.
(Other definitions for all the best that I've seen before include "Cheers" , "flower, every bit of it?" , "A greeting" , "A goodwill message" , "Pick of the bunch" .)