The most common and most likely answer to this crossword clue is the 11 plus 4 letter word WELL-EARNED REST
I've seen this crossword clue in Financial Times
W
E
L
L
-
E
A
R
N
E
D
R
E
S
T
Buddy explains!
The straight part
We know that "reward for hard wor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reward for hard wor = well-earned rest.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.