Polite to Ian, a chap who is not of service (5)
I believe the answer is:
civil
'polite' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for civil that I've seen before include "Polite to the state" , "Nonviolent refusal to obey laws" , "Mannerly" , "Courteous, polite" , "Relating to citizens" .)