The most common and most likely answer to this crossword clue is the 8 letter word OPPONENT
I've seen this crossword clue in Independent
O
P
P
O
N
E
N
T
More clues leading to the result OPPONENT
- Player against work with piano nonet being composed
- Zero pressure working in the midst of confined enemy
- Shut up about Penny performing with love rival
- Work with part containing single name for rival
- Pop off before a bid for the other side
- He’s against surgery on pet with broken back possibly
- Choose to accept P-A-N as rival?
- Covering pages one and two regularly irritated rival
- Mate initially needs ten cycles as competitor
- Round pages on English books – he’s against it!
Buddy explains!

The straight part
We know that "enemy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case enemy = opponent.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 OPPONENT mean?
OPPONENT noun- One who opposes another; one who works or takes a position against someone or something; one who attempts to stop the progress of someone or something.
- Opposing; adverse; antagonistic.
- Situated in front; opposite.