Composer having suspicion about one? Deny cut (8)
I believe the answer is:
sibelius
'composer' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
(Other definitions for sibelius that I've seen before include "Composer of Finlandia, d. 1957" , "Finnish composer, d. 1957" , "Finnish composer (Karelia Suite, Finlandia)" , "Finnish composer is strangely Isis blue" , "Isis blue (anag) - composer, d. 1957" .)