Contemptuous expression upset one Tuesday regular (7)
I believe the answer is:
habitue
'regular' is the definition.
(synonyms)
'contemptuous expression upset one tuesday' is the wordplay.
'contemptuous expression' becomes 'bah' (expression of disapproval, as in 'bah humbug!').
'upset' says the letters should be written backwards.
'one' becomes 'i' (Roman numeral).
'tuesday' becomes 'tue' (short for Tuesday).
'bah' back-to-front is 'hab'.
'hab'+'i'+'tue'='HABITUE'
(Other definitions for habitue that I've seen before include "Regular visitor (to place)" , "One of the regulars" , "Person who visits a place frequently, may live there" , "Regular attendant" , "Constant visitor" .)