Known about eccentric (5)
I believe the answer is:
outre
'eccentric' is the definition.
(I know that eccentric can be written as outre)
'known about' is the wordplay.
'known' becomes 'out' (I've seen this before).
'about' becomes 're' ('re' means regarding or about).
'out'+'re'='OUTRE'
(Other definitions for outre that I've seen before include "Bizarre or eccentric in France" , "Odd, bizarre" , "Shocking - route (anag)" , "bizarre style" , "Weird" .)