Avoid commercial during day before festival (5)
I believe the answer is:
evade
'avoid' is the definition.
(evading is a kind of avoiding)
'commercial during day before festival' is the wordplay.
'commercial' becomes 'ad'.
'during' indicates putting letters inside.
'day before festival' becomes 'eve' (I've seen this before).
'ad' placed into 'eve' is 'EVADE'.
(Other definitions for evade that I've seen before include "Escape (something)" , "skirt" , "Keep away from" , "Hedge" , "Illegally escape (taxes)" .)