Cut off some of the beams? (6)
I believe the answer is:
darken
'cut' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Perhaps you can see an association between them that I can't see?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for darken that I've seen before include "Make less light" , "Dim" , "Cast a shadow over" , "Cloud over" , "Grow blacker" .)