Grass when you have hunger? Not good! (4)
I believe the answer is:
reed
'grass' is the definition.
(I've seen this before)
'when you have hunger? not good' is the wordplay.
I cannot quite see how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is found within the answer.
The remaining letters 'red' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for reed that I've seen before include "Film director" , "Marsh plant with straight hollow stem" , "Oliver, say" , "Vibrator in the mouthpiece of a wind instrument" , "piece for organ" .)