Answer
$-\dfrac{\sqrt3}{2}$
Work Step by Step
We know that $\sin$, $\csc$, $tan$ are odd functions, which means $f(-\theta)=-f(\theta).$
We also know that $\cos$, $\sec$, are even functions, which means $f(-\theta)=f(\theta).$
Therefore,
$\sin{\left(-\frac{\pi}{3}\right)}=-\sin{\left(\frac{\pi}{3}\right)}=-\frac{\sqrt3}{2}$