The phrase "actually a challenge" is correct and usable in written English.
You can use it to emphasize that something is indeed difficult or requires effort, often in contrast to a previous assumption.
Example: "I thought the project would be easy, but it turned out to be actually a challenge."
Alternatives: "truly a challenge" or "genuinely a challenge."
Getting any work is amazing, but something which is actually a challenge really is".
It turns out it's actually a challenge to find a "C" restaurant at which to tempt fate.
Oh, and Collins has even started building a Google map based on locations in Garner's books, and has had a go at plotting the journey Colin and Susan make from Highmost Redmanhey when pursued by the powers of Nastrond … It's actually a challenge to continue writing this article instead of just filling a flask with tea, packing my boots and driving straight off to Alderley Edge.
The Apple of Eden is a device that gives a bad guy superpowers so boss fights are actually a challenge.
Full anatomic ACL reconstruction remains actually a challenge, and the best we can achieve is a compromise between anatomy, biomechanics and isometry.
An adaption of scalable workload-driven partitioning to these NoSQL data stores is actually a challenge and require minor changes for implementation.
Tim comes in and asks how everyone is doing and reminds them that even though this might seem like a lame conceptual challenge it is actually a Garnier challenge.
That can actually be a challenge in a way".
It's actually quite a challenge to love humankind in this way".
You mean this transplanted Tennessean is actually considering a challenge to Senator Kirsten E. Gillibrand in the Democratic primary?
We could struggle as the players have to get used to each other and to the new gegenpressing system, or we could hit the ground running and actually make a challenge of the season.
