There's nothing in Kenilworth (3)
I believe the answer is:
nil
'there's nothing' is the definition.
(I've seen this before)
'in kenilworth' is the wordplay.
'in' says the answer is hidden in the clue.
'NIL' is hidden in the letters of 'kenilworth'.
(Other definitions for nil that I've seen before include "none" , "Nothing found in senility" , "Zero, zilch" , "Nothing, zero" , "0" .)