The Clearance sale switch on the product in Pickware Admin shows whether Shopify keeps selling the product even without stock. It is the counterpart to the Shopify option Continue selling when out of stock, but with reversed logic.
How are Clearance sale and "Continue selling" related?
Pickware takes the value from Shopify and reverses it:
If Continue selling when out of stock is active in Shopify, Clearance sale is off in Pickware.
If the option is off in Shopify, Clearance sale is on in Pickware. Shopify then only sells the product as long as stock is available.
An active clearance sale in Pickware therefore does not mean that you are selling the product off at a particularly low price, only that Shopify does not keep selling it without stock.
Where do I change the setting?
Change the setting in Shopify on the product or on the respective variant. Pickware takes it over during the product import from Shopify. If you change the switch in Pickware Admin, this does not affect the product in Shopify. Pickware Admin points this out to you when you save.
You can find out which other product data Pickware takes over from Shopify in How do I import my products from Shopify to Pickware?.
What does Pickware use the Clearance sale for?
In demand planning, you can hide products with an active clearance sale using the Hide products in clearance sale filter. By default, this filter is off. More on this in How does demand planning work with Pickware?.