Might it be down to a change of diet? (4)
I believe the answer is:
tide
'might it be down' is the definition.
I can't judge whether this definition defines the answer.
'change of diet?' is the wordplay.
'change of' indicates anagramming the letters.
'diet' with letters rearranged gives 'TIDE'.
'to a' is the link.
Can you help me to learn more?
(Other definitions for tide that I've seen before include "Ocean phase" , "Something going in and out" , "Movement of seawater" , "Periodic flow" , "Time and it wait for no man" .)