The most common and most likely answer to this crossword clue is the 6 letter word GOONDA
G
O
O
N
D
A
More clues leading to the result GOONDA
Buddy explains!

The straight part
We know that "thug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thug = goonda.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 GOONDA mean?
GOONDA noun- A hired thug.