Was rude to a busman! (6)
I believe the answer is:
abused
'was rude' is the definition.
I can't judge whether this definition defines the answer.
'a busman' is the wordplay.
I cannot really understand how this works, but
'a' is present in the answer.
The remaining letters 'bused' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for abused that I've seen before include "were cruel to partners!" , "Ill-treated" , "Treated cruelly; insulted" , "Reviled, called nasty names" , "vilified" .)