Fashion icon ringing a doctor, part of circle (8)
I believe the answer is:
quadrant
'part of circle' is the definition.
(one of the four quarters of a circle)
'fashion icon ringing a doctor' is the wordplay.
'fashion icon' becomes 'quant' (fashion designer Mary Quant).
'ringing' means one lot of letters goes inside another.
'doctor' becomes 'Dr' (abbreviation).
'a'+'dr'='adr'
'quant' enclosing 'adr' is 'QUADRANT'.
(Other definitions for quadrant that I've seen before include "Instrument" , "Quarter of a circle or of its circumference" , "Half of a semicircle" , "Fourth part of circumference" , "One fourth of circle" .)