"It's a date!" (4)
(Other definitions for lets that I've seen before include "Leases" , "Allows or causes to" , "we shall serve them again!" , "Permits" , "Yes" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">it's a date</span>' is the definition.<br/ ><span class="explanation-format__explanation">(tryst is a kind of date)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tryst that I've seen before include "An archaic lovers' meeting" , "(Secret) meeting between lovers" , "Rendezvous with lover" , "meeting-place" , "Pre-arranged (secret) meeting" .)