Genius? Most are slammed (7)
I believe the answer is:
maestro
'genius?' is the definition.
(I've seen this before)
'most are slammed' is the wordplay.
'slammed' indicates an anagram.
'most'+'are'='mostare'
'mostare' is an anagram of 'MAESTRO'.
(Other definitions for maestro that I've seen before include "Highly talented figure in a given field" , "Distinguished artist" , "great expert" , "Wizard" , "Rattle, say" .)