The most common and most likely answer to this crossword clue is the 12 letter word REMUNERATION
I've seen this crossword clue in The Times
R
E
M
U
N
E
R
A
T
I
O
N
More clues leading to the result REMUNERATION
Buddy explains!

The straight part
We know that "reward" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reward = remuneration.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 REMUNERATION mean?
REMUNERATION noun- Something given in exchange for goods or services rendered.
- A payment for work done; wages, salary, emolument.
- A recompense for a loss; compensation.