The most common and most likely answer to this crossword clue is the 5 plus 2 letter word SCREW UP
I've seen this crossword clue in The Guardian
S
C
R
E
W
U
P
Buddy explains!

The straight part
We know that "get tight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case get tight = screw up.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 SCREW UP mean?
SCREW UP noun- A substantial mistake, usually causing problems for more people than just the person or group who made it.
- A person who often makes substantial mistakes; a bungler.
- A person who is mentally or emotionally damaged.