Vessel at Cairo museum's entrance, unusually broad (9)
I believe the answer is:
panoramic
'broad' is the definition.
(similar in meaning)
'vessel at cairo museum's entrance unusually' is the wordplay.
'vessel' becomes 'pan' (vessel or container for cooking).
'at' is a charade indicator (letters next to each other).
'entrance' says to take the initial letters.
'unusually' indicates an anagram.
The first letter of 'museums' is 'm'.
'cairo'+'m'='cairom'
'cairom' anagrammed gives 'oramic'.
'pan'+'oramic'='PANORAMIC'
(Other definitions for panoramic that I've seen before include "All-round (view)" , "offering wide views?" , "Comprehensive" , "Offering all-round views" , "Widespread" .)