The I in ICBM (5)
I believe the answer is:
inter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the i in icbm</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for inter that I've seen before include "Milan FC" , "Cover" , "Settle in ground" , "I rent (anag.)" , "somewhere between ..." .)