Strange artist keeping very quiet? I'm even quieter! (8)
I believe the answer is:
trappist
'i'm even quieter' is the definition.
(as in trappist monks)
'strange artist keeping very quiet?' is the wordplay.
'strange' indicates anagramming the letters.
'keeping' indicates putting letters inside.
'very quiet?' becomes 'pp' (musical abbreviation for pianissimo).
'artist' is an anagram of 'traist'.
'traist' enclosing 'pp' is 'TRAPPIST'.
(Other definitions for trappist that I've seen before include "Past trip (anag.)" , "who likes to be silent?" , "Monk vowed to silence" , "Member of an order of monks noted for austerity and silence" , "Quiet Man" .)