Kristin Cavallari says Morgan Wallen knows his way around the bedroom ... branding him a "great f*** buddy" -- though sounds like Morgan gets a bit of practice around Nashville.

The reality television star stopped by Bunnie Xo's “Dumb Blonde” podcast for an episode released earlier Sunday ... dishing for the first time on details of her romance with the country star. .

Watch the full clip for yourself ... Kristin says she and Morgan never really dated -- but, they started hooking up because Kristin wanted a "f*** buddy in Nashville."

Bunnie XO jokes that Morgan usually seems down to play the role ... so, sounds like Mr. Wallen's not turning down a lot of friends with benefits situations.

KC admits Morgan's a great partner when it comes to doing the nasty ... adding he's also got a really big heart.

That said, Cavallari admits Morgan not falling head over heels for her while they were together kinda threw her ... explaining she's used to having the upper hand in her romantic relationships.

Kristin first confirmed the romance with Wallen in an Instagram vid posted by friend Justin Anderson in her viral "Suspect" vid ... with Anderson saying about Kristin "Suspect let Morgan Wallen hurt her feelings, and she kept going back."