Rise and fall of poor diet (4)
I believe the answer is:
tide
'rise and fall' is the definition.
I can't tell whether this definition defines the answer.
'poor diet' is the wordplay.
'poor' indicates anagramming the letters.
'diet' anagrammed gives 'TIDE'.
'of' is the link.
Can you help me to learn more?
(Other definitions for tide that I've seen before include "Something going in and out" , "In the main, movement" , "Sea's movement" , "Moon-driven sea movement" , "turning point" .)