The most common and most likely answer to this crossword clue is the 1 plus 6 letter word A PRIORI
A
P
R
I
O
R
I
More clues leading to the result A PRIORI
- Carnival scene's penned in time for fooling theoretically
- Deduced time for pranks or indiscretions, primarily
- Men arriving in time to fool one: that’s known in advance
- First-class cases old magistrate deduced
- Theoretically, capital keeps leading man in order
- Unusually par the first: golf club detailed round without experience
- Article by monk, one deduced
- Men arriving in time to fool one in theory
- Time for fooling around carnival city, theoretically
- Boris sheds clothes on foolish date, as we may deduce
Buddy explains!

The straight part
We know that "deductive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deductive = a priori.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.