Guardian (9)
There are a few possibilities for this:
custodian
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">guardian</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that custodian is a type of guardian)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for custodian that I've seen before include "One takes care of" , "Guardian" , "Protector" , "Protector/guardian (of something)" , "museum keeper" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">guardian</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that sentry is a type of security guard)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sentry that I've seen before include "Watchperson" , "Soldier posted to keep watch" , "Mil. guard" , "Watchman" , "Person posted to keep watch for some anticipated event" .)
(Other definitions for warden that I've seen before include "Custodian" , "Guard, keeper" , "Official with supervisory duties, as in relation to a church" , "The - (Trollope)" , "Head of certain schools, colleges, etc" .)