Strains from Cadmus iconic (5)
I believe the answer is:
music
'strains' is the definition.
(I've seen this before)
'from cadmus iconic' is the wordplay.
'from' says the answer is hidden in the clue.
'MUSIC' is hidden within 'cadmus iconic'.
(Other definitions for music that I've seen before include "Staff will support this" , "Art (of noise)" , "Melodious sounds" , "Pleasant sound (to one's ears)" , "Sweet sound." .)