Commercial suitable to alter (5)
I believe the answer is:
adapt
'alter' is the definition.
(adapting is a kind of altering)
'commercial suitable' is the wordplay.
'commercial' becomes 'ad'.
'suitable' becomes 'apt' (I've seen this before).
'ad'+'apt'='ADAPT'
'to' acts as a link.
(Other definitions for adapt that I've seen before include "Adjust (to new condition)" , "Change to suit a different purpose" , "Tailor" , "Modify, adjust" , "Fashion" .)