Intended food must contain new ingredient (5)
I believe the answer is:
meant
'intended' is the definition.
(meaning is a kind of intending)
'contain new ingredient' is the wordplay.
'contain' means one lot of letters goes inside another.
'new' becomes 'n'.
'ingredient' becomes 'meat' (I can't explain this - if you can you should give a lot more credence to this answer).
'n' going inside 'meat' is 'MEANT'.
'food must' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for meant that I've seen before include "designed" , "Intentional" , "Had as purpose or design" , "Signified" , "Deliberate" .)