Diets must change with the times (5)
I believe the answer is:
tides
'the times' is the definition.
The answer and definition can be both related to natural events as well as being plural nouns.
Perhaps you can see a link between them that I can't see?
'diets must change' is the wordplay.
'must change' indicates anagramming the letters (I've seen this in other clues).
'diets' is an anagram of 'TIDES'.
'with' is the link.
Can you help me to learn more?
(Other definitions for tides that I've seen before include "Those fluctuating" , "Sited (anag.)" , "Lunar-driven ocean movements" , "Critical moments" , "They ebb and flow" .)