Half-hearted ally turns in Doncaster man (5)

I believe the answer is:
dylan
'man' is the definition.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for dylan that I've seen before include "Bob (musician) or Thomas (poet)" , "Roundabout rabbit" , "Bob Zimmerman" , "and 19: Welsh poet" , "... Thomas, Welsh writer" .)
