Just over half of the arboretum was cut back leaving them unable to speak (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
mute
'unable to speak' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for mute that I've seen before include "Silent - dumb" , "Silent, refraining from speaking" , "Not pronounced" , "Speechless, soundless" , "Silencer" .)