Limitless quantity (3)
I believe the answer is:
sea
'limitless quantity' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sea that I've seen before include "Division of an ocean" , "E.g. Baltic" , "Ocean area" , "& 14 Ozone" , "Caspian, e.g." .)