Old lady's looking sad, abandoned by a virtuoso (9)
I believe the answer is:
masterful
'virtuoso' is the definition.
(I know that virtuoso can be written as masterful)
'old lady's looking sad abandoned by a' is the wordplay.
'old lady's' becomes 'ma's' (both can informally mean mother).
'looking sad' becomes 'tearful' (you cry when you're sad).
'abandoned by' indicates named letters should be taken away.
'tearful' with 'a' taken away is 'terful'.
'mas'+'terful'='MASTERFUL'
(Other definitions for masterful that I've seen before include "Having dominating quality" , "Dominant" , "overbearing" , "expert" , "Imperious" .)