The most common and most likely answer to this crossword clue is the 4 plus 4 letter word FAIR GAME
I've seen this crossword clue in The Times
F
A
I
R
G
A
M
E
More clues leading to the result FAIR GAME
- Market willing to identify legitimate target
- Legitimate target in coconut shy, possibly?
- Fine description of Quidditch? It can reasonably be attacked
- Reasonable target in coconut shy?
- Ping pong fish bowls – a legitimate target?
- Gamble on Five’s opening song becoming a legitimate target for ridicule
- Legitimate target in ‘Splat the Rat’, say
- Aunt Sally?
- Legitimate object of ridicule in whack-a-mole?
- Just willing to be easy prey
Buddy explains!

The straight part
We know that "It can reasonably be attacked" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it can reasonably be attacked = fair game.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.