Godliness in court, within reason (8)
I believe the answer is:
sanctity
'godliness' is the definition.
(I've seen this in another clue)
'court within reason' is the wordplay.
'court' becomes 'ct' (abbreviation used in road names).
'within' is an insertion indicator.
'reason' becomes 'sanity' (I've seen this in another clue).
'ct' going inside 'sanity' is 'SANCTITY'.
'in' acts as a link.
(Other definitions for sanctity that I've seen before include "Great goodness" , "Ultimate importance" , "Condition of holiness" , "Holy or sacred state" , "Righteousness" .)