Money saved (4,3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">money saved</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 nest egg that I've seen before include "Fund put by as a reserve" , "Money kept in reserve" , "Retirement savings" , "reserves" , "Money saved for a rainy day - by bird?" .)
(Another definition for nestegg that I've seen is " savings".)