Damage most of monarch's tent (7)
I believe the answer is:
marquee
'tent' is the definition.
(marquee is a kind of tent)
'damage most of monarch's' is the wordplay.
'damage' becomes 'mar' (marring is a kind of damaging).
'most of' means to remove the last letter.
'monarch' becomes 'queen' (I've seen this before).
'queen' with its last letter removed is 'quee'.
'mar'+'quee'='MARQUEE'
(Other definitions for marquee that I've seen before include "event venue" , "Big tent" , "Large tent used for party, exhibition etc" , "Canvas pavilion" , "Elaborate tent" .)