Change people in commercial (5)
I believe the answer is:
amend
'change' is the definition.
(amending is a kind of changing)
'people in commercial' is the wordplay.
'people' becomes 'men' (men are people).
'in' means one lot of letters goes inside another.
'commercial' becomes 'ad' (abbreviation for advertisement).
'men' placed into 'ad' is 'AMEND'.
(Other definitions for amend that I've seen before include "Make small improvements to" , "Alter in writing" , "Alter in detail" , "Change to improve" , "Corrct error, make a minor aleration" .)