OK, The parse I believe is (and please correct me if I'm wrong)
Hall 'n' Oates say, avoids ways to confuse Cat Stevens mentor (9)
Hall 'n' Oates say = anagram fodder
avoids ways = extract - N E S S from this
to confuse = Anagram indicator
Cat Stevens mentor = Def
Cat Stevens is a musician who was prevalent in the 70's & 80's . He converted to Islam and changed his name to Yusif Islam and has done much work around this since.
An Islamic leader is an Ayatollah, so maybe can be construed as a Mentor to him as his religious leader.
Also, (and this is the bit that clinched it for me) Daryl Hall and John Oates - also musicians around in the late 60's, 70's and 80's had a song called
'She's gone' and they likened it to (and I loosely quote) "A funky song like a Cat Stevens number"
Hope that's correct Shooty.
I did like the clues from the rest of the setters but that one just took the edge for me this week.
Les40