Made up for deficiencies, perhaps, of sound in commercial (6)
I believe the answer is:
atoned
'made up for deficiencies perhaps' is the definition.
'sound in commercial' is the wordplay.
'sound' becomes 'tone' (tone is a kind of sound**).
'in' indicates putting letters inside.
'commercial' becomes 'ad'.
'tone' inserted within 'ad' is 'ATONED'.
'of' acts as a link.
(Other definitions for atoned that I've seen before include "Made up for past offence" , "Made up for offence or sin" , "Made up for past wrongdoing" , "Made up for, say injury" , "Made redress" .)