Yes.
When you sell an investment in stock that you own it’s known as ‘closing a position’.
You can partially close a position i.e. sell only some of the shares you own in one specific company, as long as your order meets the minimum value threshold.
Top Tip: when selling only part of your investment in a given company, consider if your remaining shares will also meet the minimum order threshold of £1 per trade, when you come to sell it (this can help avoid unnecessary fees later on).