Iris affected with bust and shoulder inflammation (8)
I believe the answer is:
bursitis
'shoulder inflammation' is the definition.
(bursitis often affects shoulders)
'iris affected with bust' is the wordplay.
'affected with' is an anagram indicator.
'iris' with its letters anagrammed with 'bust' makes 'BURSITIS'.
'and' is the link.
(Other definitions for bursitis that I've seen before include "Condition such as housemaid's knee" , "Inflammation of a shoulder joint" .)