The most common and most likely answer to this crossword clue is the 7 letter word OUTLINE
I've seen this crossword clue in Financial Times
O
U
T
L
I
N
E
More clues leading to the result OUTLINE
Buddy explains!

The straight part
We know that "schematic plan" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case schematic plan = outline.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 OUTLINE mean?
OUTLINE noun- A line marking the boundary of an object figure.
- The outer shape of an object or figure.
- A sketch or drawing in which objects are delineated in contours without shading.
- A general description of some subject.
- A statement summarizing the important points of a text.
- A preliminary plan for a project.
- (film industry) A prose telling of a story intended to be turned into a screenplay; generally longer and more detailed than a treatment.
- A setline or trotline.
- To draw an outline of.
- To summarize.