Flies before noon found in deep litter (6)
I believe the answer is:
jetsam
'deep litter' is the definition.
(items littered in the sea or 'the deep')
'flies before noon' is the wordplay.
'flies' becomes 'jets' (jetting is a kind of flying).
'before noon' becomes 'am'.
'jets'+'am'='JETSAM'
'found in' acts as a link.
(Other definitions for jetsam that I've seen before include "Floating wreckage" , "Goods thrown overboard from ship in distress" , "Goods washed ashore from shipwreck" , "it is scattered at sea" , "Goods jettisoned from a ship and washed up on shore" .)