Opposite of slow (4)
I believe the answer is:
fast
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">opposite of slow</span>' is the definition.<br/ ><span class="explanation-format__explanation">('fast' is the opposite to 'slow')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for fast that I've seen before include "Abstain from eating" , "Tight; quick" , "not lento" , "Firmly attached; rapid" , "Rapid - diet" .)