The most common and most likely answer to this crossword clue is the 7 letter word CORRODE
I've seen this crossword clue in The Daily Telegraph
C
O
R
R
O
D
E
More clues leading to the result CORRODE
- Eat away at fuel element in heart of reactor
- Staff in centre deteriorate
- Fabulous bird raised and died breaking eggs — waste
- Eat away, seeing bar in centre
- Eat away at metal bar in centre
- Substance covering pole is rust
- Eat with company, drive by the Sound
- Rod inserted into center of nuclear reactor to oxidize
Buddy explains!

The straight part
We know that "Eat away" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eat away = corrode.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 CORRODE mean?
CORRODE verb- To eat away bit by bit; to wear away or diminish by gradually separating or destroying small particles of, as by action of a strong acid or a caustic alkali.
- To consume; to wear away; to prey upon; to impair.
- To have corrosive action; to be subject to corrosion.