The most common and most likely answer to this crossword clue is the 8 letter word BACKLASH
I've seen this crossword clue in The Sunday Telegraph
B
A
C
K
L
A
S
H
More clues leading to the result BACKLASH
- Want party to exchange leaders? That’ll bring hostile reaction!
- Consequence of impact made by old ship’s cat?
- Graduate chalks off negative comments?
- Adverse reaction caused by Spooner’s need to strike
- Adverse reaction, as German behind bars injects man with vaccine from behind
- Want party to change leaders? That’ll create repercussion
- Violent reaction against a flogging?
- Support whip producing retaliation
- Support painful punishment that produces strong reaction
- Adverse reaction feared by galley slave?
Buddy explains!

The straight part
We know that "strong reaction" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strong reaction = backlash.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 BACKLASH mean?
BACKLASH noun- A sudden backward motion.
- A negative reaction, objection or outcry, especially of a violent or abrupt nature.
- The distance through which one part of connected machinery, as a wheel, piston, or screw, can be moved without moving the connected parts, resulting from looseness in fitting or from wear.
- The jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion.
- To cause or set off a backlash.