The most common and most likely answer to this crossword clue is the 8 letter word UNFREEZE
I've seen this crossword clue in The Daily Telegraph
U
N
F
R
E
E
Z
E
Buddy explains!

The straight part
We know that "Remove a restriction on" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case remove a restriction on = unfreeze.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 UNFREEZE mean?
UNFREEZE verb- To defrost something.
- To thaw.
- To resume movement.
- To release from a previously locked or frozen state.