Tailors fitting in commercials (6)
I believe the answer is:
adapts
'tailors' is the definition.
(I've seen this in another clue)
'fitting in commercials' is the wordplay.
'fitting' becomes 'apt' (both mean appropriate).
'in' means one lot of letters goes inside another.
'commercials' becomes 'ads' (advertisements).
'apt' going into 'ads' is 'ADAPTS'.
(Other definitions for adapts that I've seen before include "Alters to suit new conditions" , "Converts to another use or purpose" , "Alters to suit another purpose" , "Changes to suit another purpose" , "Modifies for a new use" .)