The most common and most likely answer to this crossword clue is the 6 letter word OTITIS
I've seen this crossword clue in The Guardian
O
T
I
T
I
S
More clues leading to the result OTITIS
- Onset of obesity on monkeys leads to complaint in pavilion
- Lovebirds catching one painful inflammation
- Ear inflammation aggravated, so it doubled
- Arrowroot, it isn’t containing inflammation
- How Cockney may comment on high temperature creates a problem for the listener!
- Inflammation of the ear? It is to be treated
- Complaint comes up, therefore swallows it twice
- Tot is possibly having bit of inner ear infection
- Complaint over fliers seen around Italy
Buddy explains!

The straight part
We know that "painful inflammation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case painful inflammation = otitis.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 OTITIS mean?
OTITIS noun- Inflammation of the ear.