Searching for monarch behind throne (7)
I believe the answer is:
looking
'searching' is the definition.
('look' can be a synonym of 'search')
'monarch behind throne' is the wordplay.
'monarch' becomes 'king' (king is a kind of monarch).
'behind' means one lot of letters go next to another.
'throne' becomes 'loo' (both can mean a toilet).
'king' put after 'loo' is 'LOOKING'.
'for' acts as a link.
(Other definitions for looking that I've seen before include "Viewing" , "Watching" , "Observing" , "Appearing (like)" , "Seeming, appearing" .)