Joker in a row again (3)
I believe the answer is:
wag
'joker' is the definition.
(I've seen this before)
'in a row again' is the wordplay.
'in' indicates the answer is hidden within the clue.
'WAG' is hidden within 'row again'.
(Other definitions for wag that I've seen before include "Comedian" , "Move from side to side like dog's tail" , "Move briskly to and fro" , "Oscillate - wit" , "Person fond of tricks and playing jokes" .)