Hi Oleg Ilin,
This functionality is easily achievable with the --smart-icon--arrow-down CSS variable.
Quick code snippet that I have made to showcase you how to set it up:

smart-grid {
  height: auto;
  width: 100%;
  --smart-icon-arrow-down: var(--smart-icon-clock);

Let me know if that works for you!
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team