Spot woman's instrument (6)
I believe the answer is:
zither
'instrument' is the definition.
(I know that zither is a type of stringed instrument)
'spot woman's' is the wordplay.
'spot' becomes 'zit' (spot on one's body).
'woman' becomes 'her' (her refers to a woman).
'zit'+'her'='ZITHER'
(Other definitions for zither that I've seen before include "Stringed box, played with plectrum" , "Metal-stringed soundbox" , "Plucked musical instrument" , "Harp-like instrument" , "Stringed instrument laid flat to play" .)