Upsetting Dan and Mary Carter (7)
I believe the answer is:
drayman
'carter' is the definition.
(I've seen this before)
'upsetting dan and mary' is the wordplay.
'upsetting' indicates an anagram.
'and' means one lot of letters go next to another.
'dan' after 'mary' is 'marydan'.
'marydan' anagrammed gives 'DRAYMAN'.
(Other definitions for drayman that I've seen before include "Horse-drawn cart driver" , "Carter" .)