The most common and most likely answer to this crossword clue is the 7 letter word FATCATS
I've seen this crossword clue in Financial Times
F
A
T
C
A
T
S
Buddy explains!
The straight part
We know that "Bigwigs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bigwigs = fatcats.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 FATCATS mean?
FATCATS noun- A rich person who contributes to a political campaign.
- Any affluent person who is perceived to have profited from the labour of others.