Commercial deserved tweak (6)
I believe the answer is:
adjust
'tweak' is the definition.
'commercial deserved' is the wordplay.
'commercial' becomes 'ad'.
'deserved' becomes 'just' (I've seen this before).
'ad'+'just'='ADJUST'
(Other definitions for adjust that I've seen before include "Adapt, regulate" , "Make slight corrections to" , "Make small changes" , "Arrange, put into proper position" , "Fine-tune" .)