The most common and most likely answer to this crossword clue is the 14 letter word ACCOMPLISHMENT
I've seen this crossword clue in The Sunday Telegraph
A
C
C
O
M
P
L
I
S
H
M
E
N
T
More clues leading to the result ACCOMPLISHMENT
Buddy explains!

The straight part
We know that "exploit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case exploit = accomplishment.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 ACCOMPLISHMENT mean?
ACCOMPLISHMENT noun- The act of accomplishing; completion; fulfilment.
- That which completes, perfects, or equips thoroughly; acquirement; attainment; that which constitutes excellence of mind, or elegance of manners, acquired by education or training.
- Something accomplished; an achievement.
- (grammar) The lexical aspect (aktionsart) of verbs or predicates that change over time until a natural end point.