The most common and most likely answer to this crossword clue is the 16 letter word ACROSS-THE-BOARD
I've seen this crossword clue in Independent
A
C
R
O
S
S
-
T
H
E
-
B
O
A
R
D
More clues leading to the result ACROSS-THE-BOARD
- General initially aiming to oppose governors?
- Blanket over table?
- Where chess players may be sweeping
- Comprehensive school had Serbo-Croat Society
- A mongrel had to be ordered to cover king in blanket
- How Anand and Carlsen compete is affecting everyone
- How chess players move the men
- A plus B - carrying article by road transport uniformly
- A vote by directors affecting everyone
- Sweeping most of theatre stage after a mule, say
Buddy explains!

The straight part
We know that "Sweeping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sweeping = across-the-board.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 ACROSS-THE-BOARD mean?
ACROSS-THE-BOARD adjective- Wide or comprehensive in scope or applicability.