Opt to work with a staple food (6)
I believe the answer is:
potato
'staple food' is the definition.
(I've seen this before)
'opt to work with a' is the wordplay.
'work with' indicates an anagram.
'opt'+'to'='optto'
'optto' with its letters anagrammed with 'a' gives 'POTATO'.
(Other definitions for potato that I've seen before include "Would be difficult to deal with if hot" , "Murphy (informal)" , "Root crop" , "The humble spud" , "The veg is too apt, oddly" .)