The most common and most likely answer to this crossword clue is the 6 letter word UNSEXY
I've seen this crossword clue in The Times
U
N
S
E
X
Y
Buddy explains!
The straight part
We know that "missing out on 28?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case missing out on 28? = unsexy.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 UNSEXY mean?
UNSEXY adjective- Not sexy.
- (of research etc) Perceived as not having wide contemporary interest; plodding.