Doctor depicts pain involving bit of intestine with this complaint (12)
I believe the answer is:
appendicitis
'this complaint' is the definition.
(appendicitis is a kind of health problem)
'doctor depicts pain involving bit of intestine' is the wordplay.
'doctor' indicates anagramming the letters.
'involving' means one lot of letters goes inside another.
'bit of' indicates taking the first letters.
The first letter of 'intestine' is 'i'.
'depicts'+'pain'='depictspain'
'depictspain' anagrammed gives 'appendicits'.
'appendicits' going around 'i' is 'APPENDICITIS'.
'with' acts as a link.
(Other definitions for appendicitis that I've seen before include "Inflammation of a sac attached to the large intestine" , "complaint" , "Inflammation of intestinal sac" , "Inflammation of abdominal sac" , "Inflammation for which operation may be needed" .)