Sea in northern Europe (6)
I believe the answer is:
baltic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sea in northern europe</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for baltic that I've seen before include "Near-landlocked sea of N Europe" , "water, lots" , "Near land-locked sea of Scandinavia" , "Northern European sea" , "Nearly land-locked sea of Scandinavia" .)