Its trend is disposed to be unpleasantly harsh (8)
I believe the answer is:
strident
'unpleasantly harsh' is the definition.
'strident' can be an answer for 'harsh' (I've seen this before). I am not sure about the 'unpleasantly' bit.
'its trend is disposed' is the wordplay.
'is disposed' indicates an anagram.
'its'+'trend'='itstrend'
'itstrend' is an anagram of 'STRIDENT'.
'to be' acts as a link.
Can you help me to learn more?
(Other definitions for strident that I've seen before include "Offensively loud and harsh" , "Unpleasantly rough" , "Raucous" , "With a loud, harsh voice" , "Shrill" .)