It's Let It Be that concludes this great live event (4)
I believe the answer is:
stet
'it's let it be' is the definition.
(printing instruction to let a piece of text stand)
'that concludes this great live event' is the wordplay.
'that concludes' suggests the final letters (concluding letters).
The final letters of 'this great live event' are 'STET'.
(Other definitions for stet that I've seen before include "'Let it stand, in printing (4)'" , "Cancellation of correction" , "Instruction to keep" , "Leave in, as text" , "cancel amendment" .)