The most common and most likely answer to this crossword clue is the 6 letter word PRUNED
I've seen this crossword clue in The Times
P
R
U
N
E
D
Buddy explains!

The straight part
We know that "cut back" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cut back = pruned.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PRUNED mean?
PRUNED verb- To become wrinkled like a dried plum, as the fingers and toes do when kept submerged in water.
- To remove excess material from a tree or shrub; to trim, especially to make more healthy or productive.
- To cut down or shorten (by the removal of unnecessary material).
- To remove unnecessary branches from a tree data structure.
- To preen; to prepare; to dress.