The most common and most likely answer to this crossword clue is the 7 letter word SHELTER
I've seen this crossword clue in The Guardian
S
H
E
L
T
E
R
More clues leading to the result SHELTER
- Without qualification accepts lieutenant in refuge
- Female lieutenant going to monarch for protection
- Change course accommodating lieutenant in refuge
- Absolute protection for military officer in refuge
- Woman before reform not having a refuge
- Covering lieutenant’s rank being put up
- Put up security
- Lets her off in refuge
- Sun tans leather, not a hide
- Clear around sides of lightweight screening structure
Buddy explains!

The straight part
We know that "Put up/security" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case put up/security = shelter.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 SHELTER mean?
SHELTER noun- A refuge, haven or other cover or protection from something.
- An institution that provides temporary housing for homeless people, battered women etc.
- To provide cover from damage or harassment; to shield; to protect.
- To take cover.