Rhapsodic form of modern music, conclusion for concert (4)
I believe the answer is:
rapt
'rhapsodic' is the definition.
(thesaurus)
'conclusion for concert' is the wordplay.
'conclusion' suggests the final letters (I've seen 'conclusions of' mean this).
'concert' becomes 'apt' (I can't justify this - if you can you should believe this answer much more).
The final letter of 'for' is 'r'.
'r'+'apt'='RAPT'
'form of modern music' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
(Other definitions for rapt that I've seen before include "Part (anag.)" , "Spellbound, enthralled" , "Absorbed, fascinated" , "Held spellbound" , "Wholly engrossed" .)