The most common and most likely answer to this crossword clue is the 9 letter word ANNUITANT
I've seen this crossword clue in Financial Times
A
N
N
U
I
T
A
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T
Buddy explains!
The straight part
We know that "he’s getting a fixed income" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case he’s getting a fixed income = annuitant.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 ANNUITANT mean?
ANNUITANT noun- The recipient of an annuity.