The most common and most likely answer to this crossword clue is the 5 letter word DOWDY
D
O
W
D
Y
Buddy explains!

The straight part
We know that "old-fashioned" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old-fashioned = dowdy.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 DOWDY mean?
DOWDY noun- A plain or shabby person
- Plain and unfashionable in style or dress.
- Lacking stylishness or neatness; shabby.