Brass player has run up to Rob (6)
I believe the answer is:
burgle
'rob' is the definition.
(I've seen this in another clue)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for burgle that I've seen before include "Steal (from a house etc)" , "Enter building to steal" , "Break in to 17 dn" , "Break in and steal" , "do so is illegal!" .)