Blamelessness of civil engineer visiting pub in the past (9)
I believe the answer is:
innocence
'blamelessness' is the definition.
(I've seen this in another clue)
'civil engineer visiting pub in the past' is the wordplay.
'civil engineer' becomes 'CE' (abbreviation).
'visiting' is an insertion indicator.
'pub' becomes 'inn' (an inn is a type of pub).
'in the past' becomes 'once' (once upon a time).
'inn'+'once'='innonce'
'ce' placed into 'innonce' is 'INNOCENCE'.
'of' acts as a link.
(Other definitions for innocence that I've seen before include "clean?" , "Absence of guilt" , "subject of Blake's songs" , "Absence of sin" , "Honesty" .)