Jazz trumpeter Davis (5)
I believe the answer is:
miles
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">jazz trumpeter davis</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for miles that I've seen before include "Distance units" , "'But I have promises to keep, and . . . . . to go before I sleep' (Frost)" , "Imperial units of length" , "a long way" .)