Open tart (4)
I believe the answer is:
flan
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">open tart</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a flan is an open-topped pastry)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for flan that I've seen before include "it may get jammed" , "Open tart with a sweet or savoury filling" , "pudding!" , "Open pastry or sponge case with tasty filling" , "Open pastry dish" .)