The most common and most likely answer to this crossword clue is the 5 plus 4 letter word SOUTH POLE
I've seen this crossword clue in The Daily Telegraph
S
O
U
T
H
P
O
L
E
More clues leading to the result SOUTH POLE
- Ill-frequented locale where forbidden sauce is stuffed into fish
- Where a map-reader’s only way is up
- Building plot with house down under?
- You can only go north from here
- Hot soup dished out by the French in a cold location
- Banned brown sauce in fish where seas freeze
- Where 17 and 25 were headed, only carrying unfashionable sauce
Buddy explains!

The straight part
We know that "Where a map-reader’s only way is up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where a map-reader’s only way is up = south pole.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.