This post shows how to remove the extra line from text that has been pasted into Word from Linux. The method here also answers the question: "how do I just replace text in what I've selected."
1. Select the text
2. Click Replace in Word
3. Set Find what: to ^p in the Find and Replace window
This is a Paragraph Mark
4. Set Replace with: to ^l in the Find and Replace window
This is a Manual Line Break
5. Click Replace All
6. Decline replacing text in the rest of the document.
Word image from [link]