Tunny (4)
I believe the answer is:
tuna
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tunny</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that tunny can be written as tuna)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tuna that I've seen before include "Type of fish" , "Warm-water food fish" , "Species of fish" , "Fish; edible cactus" , "Widely-eaten fish" .)