The most common and most likely answer to this crossword clue is the 6 letter word BANTAM
I've seen this crossword clue in The Times
B
A
N
T
A
M
More clues leading to the result BANTAM
- Outlaw thanks male, an aggressive little sort
- Refuse to allow tailless domesticated fowl
- This boxer is chicken
- Aggressive person from suburban Tamworth
- Insect swallowed by black American bird
- Small soldier has trimmed ribbon on cap
- Little but combative Scotsman supports prohibition
- Small message prohibiting certain headgear
- Outlaw thanks farm finally for fowl
- Outlaw, almost docile, is chicken
Buddy explains!

The straight part
We know that "an aggressive little sort" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an aggressive little sort = bantam.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 BANTAM mean?
BANTAM noun- Any of several small chickens, especially of a breed that is a miniature version of another breed.
- A competitor in an age division between peewee and midget.
- Small or miniature.
- Spirited or aggressive.