Complaint the German’s missing problem with train (7)
I believe the answer is:
ailment
'complaint' is the definition.
(synonyms)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ailment that I've seen before include "Tim Alen has an odd indisposition." , "Physical disorder" , "problem" , "Bodily disorder or disease" , "Sickness" .)