Spot stringed instrument without her (3)
I believe the answer is:
zit
'spot' is the definition.
(spot on one's body)
'stringed instrument without her' is the wordplay.
'stringed instrument' becomes 'zither' (type of musical instrument).
'without' is a deletion indicator.
'zither' with 'her' taken away is 'ZIT'.
(Other definitions for zit that I've seen before include "Spot (colloq., mostly US)" , "Pimple (US)" , "Spot or pimple" .)