"Could you repeat that?" (4)
'could you repeat that?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for what that I've seen before include "Eh?" , "That which - come again!" , "I didn't hear" , "Which thing?" , "Word used in a question" .)
(Other definitions for come again that I've seen before include "return invitation" , "eh?" , "Turn out once more" , "You're welcome to return - pardon?" , "What did you say? - egomaniac (anag)" .)