The most common and most likely answer to this crossword clue is the 6 letter word SPRAIN
I've seen this crossword clue in The Daily Telegraph
S
P
R
A
I
N
More clues leading to the result SPRAIN
- Sign of injury from run in country
- Injury in country when crossing river
- Resistance in European nation is a joint problem
- Run in country producing damage to ankle
- Betting fall can cause injury
- European country imprisons king? That’s a wrench
- Damage when river floods country
- Country accepted Republican twist?
- Turn right visiting the Alhambra, perhaps?
- Pops back to collect gunners’ wrench
Buddy explains!

The straight part
We know that "Painful injury" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case painful injury = sprain.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 SPRAIN mean?
SPRAIN noun- The act or result of spraining; lameness caused by spraining
- To weaken, as a joint, ligament, or muscle, by sudden and excessive exertion, as by wrenching; to overstrain, or stretch injuriously, but without luxation