I’ve been searching for a bit and figured I’d ask y’all.
A cluster?
I’d say a grove
Copse, perhaps.
A stand, group, troop, copse or grove depending on the specifics.
How about “copse” (a small group of trees)
https://dictionary.cambridge.org/us/dictionary/english/copse
Copse was my initial thought, but there is also the word Spinney.