Gosh! So polite? (8)
I believe the answer is:
gracious
This clue is a double definition.
'gosh' is the first definition.
(I've seen this before)
'polite?' is the second definition.
(similar in meaning)
'so' is the link.
(Other definitions for gracious that I've seen before include "Courteous, kind, pleasant" , "Well-mannered" , "Gosh" , "Showing qualities associated with good taste and manners" , "polite expression of surprise" .)