Dad's Army (4,5)
I believe the answer is:
home guard
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dad's army</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 home guard that I've seen before include "Volunteer force" , "Dad's Army" , "security force" , "World War Two defence organisation" , "Last line of defence in World War II" .)