The most common and most likely answer to this crossword clue is the 8 letter word REQUIRED
I've seen this crossword clue in Financial Times
R
E
Q
U
I
R
E
D
More clues leading to the result REQUIRED
- Cherry-bound paper needed
- Leaves visibly embarrassed hosts with no other option?
- Obligatory papers marked urgent, it’s suggested?
- Ordered 24 sheets in colour
- Introduction of rule queried, dubiously mandatory
- Obligatory paper in colour
- Needed to be filled up with paper again?
- Needed some paper in colour
- Needed 24 sheets in crimson
Buddy explains!

The straight part
We know that "Obligator" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case obligator = required.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.
What does REQUIRED mean?
REQUIRED verb- To ask (someone) for something; to request.
- To demand, to insist upon (having); to call for authoritatively.
- Naturally to demand (something) as indispensable; to need, to call for as necessary.
- To demand of (someone) to do something.
- Necessary; obligatory; mandatory.