Tweak food from time to time, providing cracking goodness (6)
I believe the answer is:
modify
'tweak' is the definition.
(I've seen this in another clue)
'food from time to time providing cracking goodness' is the wordplay.
'from time to time' means one should take alternating letters (letters removed on a regular basis).
'providing' becomes 'if' (eg 'providing it's sunny' means 'if it's sunny').
'cracking' indicates putting letters inside (inserted letters go into a gap or crack).
'goodness' becomes 'my' (both are exclamations of surprise).
The alternate letters of 'food' are 'od'.
'od'+'if'='odif'
'odif' placed inside 'my' is 'MODIFY'.
(Other definitions for modify that I've seen before include "temper" , "Adjust" , "reform" , "Alter slightly" , "Reshape" .)