Flood medium with dairy product (6)
I believe the answer is:
myriad
'flood' is the definition.
(thesaurus)
'medium with dairy product' is the wordplay.
I cannot really see how this works, but
'medium' could be 'm' (as in UK clothing sizes) and 'm' is found within the answer.
an anagram of 'dairy' is 'yriad' which is within the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for myriad that I've seen before include "Lots of" , "Too numerous to be counted" , "Host" , "immense quantity" , "Numberless" .)