Become less neat (5)
I believe the answer is:
lower
'become' is the definition.
The answer and definition can be both related to change as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lower that I've seen before include "where are trousers in relation?" , "Hereford, say" , "Threaten" , "Take down" , "Bring down" .)