One sells food Tue-Fri for cooking, with arrears off and on (9)
I believe the answer is:
fruiterer
'one sells food' is the definition.
(someone who sells fruit)
'tue-fri for cooking with arrears off and on' is the wordplay.
'for cooking with' indicates an anagram.
'off and on' indicates alternate letters (letters used at regular intervals).
The alternating letters of 'arrears' are 'rer'.
'tue'+'fri'='tuefri'
'tuefri' with its letters mixed up with 'rer' makes 'FRUITERER'.
(Other definitions for fruiterer that I've seen before include "Greengrocer" , "Dealer in produce" , "Dealer in apples and pears?" .)