The most common and most likely answer to this crossword clue is the 7 letter word BOWLERS
B
O
W
L
E
R
S
More clues leading to the result BOWLERS
Buddy explains!

The straight part
We know that "hats" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hats = bowlers.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 BOWLERS mean?
BOWLERS noun- One who engages in the sport of bowling.
- The player currently bowling.
- A player selected mainly for his bowling ability.
- (1800s) The pitcher.
- A bowler hat; a round black hat formerly popular among British businessmen.