More nuts ruin an ersatz slice (6)
I believe the answer is:
inaner
'more nuts' is the definition.
(I've seen this in another clue)
'ruin an ersatz slice' is the wordplay.
'slice' indicates a hidden word.
'INANER' is hidden in the letters of 'ruin an ersatz'.
(Other definitions for inaner that I've seen before include "More vacuous" , "Rather silly" , "More empty" , "What's relatively lemon-like" , "More stupid" .)