Could be soft on her, silly, silly sap! (7)
I believe the answer is:
perhaps
'could be' is the definition.
I can't judge whether this defines the answer.
'soft on her silly silly sap' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'on' means one lot of letters goes inside another (as in clothing \'on\' a person).
'silly' is an anagram indicator.
'silly' is an anagram indicator.
'her' with letters rearranged gives 'erh'.
'sap' with letters rearranged gives 'aps'.
'erh' put within 'aps' is 'erhaps'.
'p'+'erhaps'='PERHAPS'
Can you help me to learn more?
(Other definitions for perhaps that I've seen before include "Could be, maybe" , "Not necessarily" , "Possibly but not certainly" , "It may be" , "Quite possibly" .)