Correct people used in the commercial (5)
I believe the answer is:
amend
'correct' is the definition.
(amending is a kind of correcting)
'people used in the commercial' is the wordplay.
'people' becomes 'men' (men are people).
'used in' indicates putting letters inside.
'the commercial' becomes 'ad' (abbreviation for advertisement).
'men' inserted into 'ad' is 'AMEND'.
(Other definitions for amend that I've seen before include "Rectify" , "Correct or alter to improve" , "Ameliorate" , "Make minor improvements to (a document)" , "Change to improve" .)