Sauce only served in pub by church (9)
I believe the answer is:
Here is my best explanation:
'sauce' is the definition.
'only served in pub by church' is the wordplay.
'only' becomes 'sole' ('sole' can be a synonym of 'only').
'served in' indicates putting letters inside.
'pub' becomes 'inn' (I've seen this before).
'by' means one lot of letters go next to another.
'church' becomes 'ce' (abbreviation for Church of England).
'sole' put inside 'inn' is 'insolen'.
(Other definitions for insolence that I've seen before include "Impertinence, impudence", "lack of respect", "Disrespectful behaviour", "Rudeness, impudence", "Disrespect", "Rudeness, disrespect", "Rude behaviour", "Lip; cheek", "Sauce" and "Front".)