Salty bleed at sea? Flogging should not happen after this (4-2,4)
I believe the answer is:
sell-by date
'flogging should not happen after this' is the definition.
(date an item shouldn't be sold or flogged after)
'salty bleed at sea?' is the wordplay.
'at sea?' indicates an anagram (I've seen 'at sea' mean this).
'salty'+'bleed'='saltybleed'
'saltybleed' with letters rearranged gives 'SELL-BY-DATE'.
(Other definitions for sell-by date that I've seen before include "Perishable deadline" , "Mark on a perishable" , "Food shop marking" .)