Part of the route runs well away from the bull! (5)
I believe the answer is:
outer
'part' is the definition.
(I have seen 'part of target' mean 'outer' so perhaps 'part' could also mean 'outer')
'the route runs well away from the bull' is the wordplay.
'route' anagrams to 'OUTER'.
But, I'm unsure how this is indicated.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for outer that I've seen before include "Ring furthest from the bullseye" , "External; part of archery target" , "External kind of route" , "Surrounding" , "Objective" .)