The most common and most likely answer to this crossword clue is the 8 letter word TRANSFIX
I've seen this crossword clue in The Daily Telegraph
T
R
A
N
S
F
I
X
Buddy explains!
The straight part
We know that "Grip" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case grip = transfix.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 TRANSFIX mean?
TRANSFIX verb- To render motionless, by arousing terror, amazement or awe.
- To pierce with a sharp pointed weapon.
- To fix or impale.
- A discontinuous affix, which occurs at more than one position in a word, typical of Semitic languages.