The most common and most likely answer to this crossword clue is the 5 letter word QUILT
I've seen this crossword clue in The Guardian
Q
U
I
L
T
Buddy explains!

The straight part
We know that "cover for retirement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cover for retirement = quilt.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 QUILT mean?
QUILT noun- A bed covering consisting of two layers of fabric stitched together, with insulation between, often having a decorative design.
- A roll of material with sound-absorbing properties, used in soundproofing.
- A quilted skirt worn by women.
- To construct a quilt.
- To construct something, such as clothing, using the same technique.