There's nothing like a Japanese fighter! (4)
I believe the answer is:
zero
'a japanese fighter' is the definition.
(I've seen this before)
'there's nothing like' is the wordplay.
'there's' says to put letters next to each other.
'nothing' becomes 'z'.
'like' becomes 'ero' (I am not sure about this - if you are sure you should believe this answer much more).
'z' put next to 'ero' is 'ZERO'.
Can you help me to learn more?
(Other definitions for zero that I've seen before include "[NIX]" , "See 22" , "Uncompromising application of the law against antisocial behaviour" , "Nonentity" , "Nought, nothing" .)