Be lost, like a monarch in a shipwreck (6)
I believe the answer is:
perish
'be lost' is the definition.
(thesaurus)
'a monarch in a shipwreck' is the wordplay.
'a monarch' becomes 'ER' (abbreviation for Elizabeth Regina, British Queen).
'in' means one lot of letters goes inside another.
'a shipwreck' becomes 'pish' (anagram of 'ship').
'er' inserted into 'pish' is 'PERISH'.
'like' is the link.
(Other definitions for perish that I've seen before include "Deteriorate, rot" , "Pass away" , "Die; decay" , "Suffer complete ruin or destruction" , "Expire" .)