The phrase "already cluttered" is correct and usable in written English.
It can be used to describe a situation or space that is filled with too many items or distractions at a given point in time.
Example: "The desk was already cluttered with papers and office supplies, making it difficult to find the important documents."
Alternatives: "already messy" or "already disorganized".
The room was already cluttered with draft treaties, notes and coffee cups.
But, with the hippies' departure from the already cluttered brownstone, the brothers' "abandonment of the outer world" becomes irreversible.
To establish the festival as a perennial event, the city must also muscle its way into an already cluttered film festival and market calendar.
Even though the vodka category is already cluttered, Mr. Roux is optimistic that he can work his marketing magic once again.
There was a subtle sense of frustration among some consumers that they were being asked to bring yet another expensive device into lives already cluttered with finger-smudged screens and tangled power cords.
Strap a polygraph to Sir Alex Ferguson and he might just be forced to admit that he often finds the Carling Cup a hindrance in an already cluttered fixture list.
"Just to clarify," I added, looking at Clementine, "the last thing we need is more computer games or videos, the stuff that's already cluttering the house".
It's also strong on data systems and coordination of the myriad programs that already clutter this field.
The Group D table has already become cluttered.
It means opting in for more advertising, cluttering up an already-cluttered News Feed and irritating all the friends who'll soon get pitches from whatever brand you've "liked".
The stage of the Joyce, already small, was cluttered with big photos of Glover's heroes (Gandhi, Gregory Hines, Bunny Briggs, et al)., platforms on which his dance students struck Zen poses, and more votive candles than you've ever seen in your life.
