Dan must change profession (7)
I believe the answer is:
dustman
'profession' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'dan must change' is the wordplay.
'change' indicates an anagram.
'dan'+'must'='danmust'
'danmust' with letters rearranged gives 'DUSTMAN'.
Can you help me to learn more?
(Other definitions for dustman that I've seen before include "I clear what's left" , "Refuse worker" , "Bin emptier" , "Rubbish collector" , "Garbage collector" .)