What does the cryptic crossword clue "A cur hit me unexpectedly and I'm in pain (9)" mean?

The definition is "pain". The wordplay uses an anagram. anagram of A CUR HIT ME = RHEUMATIC The answer is RHEUMATIC.

A cur hit me unexpectedly and I'm in pain (9)

Guardian Cryptic #25225 | 15 Down | 2011-01-21 flower